Weight Conversion Guide

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Convert between all weight units — kilograms, tonnes, pounds, grams & more. Plus estimate material weight by volume for concrete, steel, sand, and aggregates.

Weight Unit Conversion & Material Weight Guide

This free weight conversion guide lets you instantly convert between all major metric and imperial weight units — kilograms (kg), metric tonnes, grams, milligrams, micrograms, pounds (lb), ounces (oz), US tons, UK (long) tons, and carats. All conversions are based on exact SI definitions and international measurement standards fromBIPM (Bureau International des Poids et Mesures).

TheMaterial Weight Guidebelow goes further — enter a volume in cubic metres, cubic feet, or litres and instantly find the mass of concrete, reinforced concrete, structural steel, water, sand, gravel, soil, asphalt, and many more common construction and civil engineering materials. Densities are referenced fromEngineering Toolbox, IS 875 Part 1 (Dead Loads), and BS EN 1991-1-1 (Eurocode 1).

Charts and tables on this page cover all standard weight conversion factors, material densities for construction and industrial applications, and worked examples for common engineering problems.

Live Weight Unit Conversion guide — All Units

Weight / Mass Conversion guide

Material Weight Guide — Concrete, Steel, Sand & More

Enter the volume of material and instantly estimate its mass. Densities are per IS 875 Part 1:1987 (Dead Loads), BS EN 1991-1-1 (Eurocode 1), and standard engineering references.

Volume → Mass Guide

ℹ️ Densities shown are typical values for standard conditions. Actual values vary with moisture content, grading, compaction, and temperature. For structural design, always use values from project specifications or material test certificates.

Material Density Chart — Weight per Cubic Metre (kg/m³)

Comparative densities of common construction, engineering, and industrial materials per IS 875 Part 1, BS EN 1991-1-1 (Eurocode 1), and standard engineering references. Higher density = heavier material per unit volume.

Complete Weight Unit Conversion Factor Table — kg Reference

All weight units expressed as their exact equivalent in kilograms (kg). Multiply the given quantity by the factor to convert to kg. To convert from kg, divide by the factor. All values per SI and NIST standards.

  • Unit Name: Kilogram; Symbol: kg; System: SI (Metric); Exact Value in kg: 1 kg (base unit); 1 kg Equals: 1.000 kg; Common Use: Universal standard unit of mass
  • Unit Name: Metric Tonne; Symbol: t; System: SI (Metric); Exact Value in kg: 1,000 kg; 1 kg Equals: 0.001 t; Common Use: Civil engineering, bulk materials, freight
  • Unit Name: Gram; Symbol: g; System: SI (Metric); Exact Value in kg: 0.001 kg; 1 kg Equals: 1,000 g; Common Use: Food, laboratory, medicine
  • Unit Name: Milligram; Symbol: mg; System: SI (Metric); Exact Value in kg: 0.000001 kg; 1 kg Equals: 1,000,000 mg; Common Use: Pharmaceuticals, chemistry
  • Unit Name: Microgram; Symbol: µg; System: SI (Metric); Exact Value in kg: 0.000000001 kg; 1 kg Equals: 1×10⁹ µg; Common Use: Laboratory analysis, pollution measurement
  • Unit Name: Quintal; Symbol: q; System: Metric; Exact Value in kg: 100 kg; 1 kg Equals: 0.01 q; Common Use: Agriculture (India, Europe)
  • Unit Name: Pound; Symbol: lb; System: Imperial / US; Exact Value in kg: 0.45359237 kg; 1 kg Equals: 2.204623 lb; Common Use: US everyday, UK general use
  • Unit Name: Ounce; Symbol: oz; System: Imperial / US; Exact Value in kg: 0.028349523 kg; 1 kg Equals: 35.27396 oz; Common Use: US food, UK retail
  • Unit Name: US Short Ton; Symbol: ton (US); System: US Customary; Exact Value in kg: 907.18474 kg; 1 kg Equals: 0.001102 US tons; Common Use: US freight, mining, agriculture
  • Unit Name: UK Long Ton; Symbol: ton (UK); System: Imperial; Exact Value in kg: 1,016.04691 kg; 1 kg Equals: 0.000984 UK tons; Common Use: UK shipping, historical engineering
  • Unit Name: Stone; Symbol: st; System: Imperial (UK); Exact Value in kg: 6.35029 kg; 1 kg Equals: 0.157473 stone; Common Use: UK body weight measurement
  • Unit Name: Grain; Symbol: gr; System: Imperial; Exact Value in kg: 0.00006479891 kg; 1 kg Equals: 15,432.36 gr; Common Use: Bullets, gunpowder, pharmacy
  • Unit Name: US Hundredweight; Symbol: cwt (US); System: US Customary; Exact Value in kg: 45.359237 kg; 1 kg Equals: 0.022046 US cwt; Common Use: US agriculture, coal, commodities
  • Unit Name: UK Hundredweight; Symbol: cwt (UK); System: Imperial; Exact Value in kg: 50.80235 kg; 1 kg Equals: 0.019684 UK cwt; Common Use: UK historical trade
  • Unit Name: Carat; Symbol: ct; System: Gemological; Exact Value in kg: 0.0002 kg; 1 kg Equals: 5,000 ct; Common Use: Gemstones, diamonds
  • Unit Name: Troy Ounce; Symbol: troy oz; System: Troy; Exact Value in kg: 0.0311034768 kg; 1 kg Equals: 32.1507 troy oz; Common Use: Gold, silver, precious metals
  • Unit Name: Troy Pound; Symbol: troy lb; System: Troy; Exact Value in kg: 0.3732417216 kg; 1 kg Equals: 2.67923 troy lb; Common Use: Precious metals, pharmacy history
  • Unit Name: Pennyweight; Symbol: dwt; System: Troy; Exact Value in kg: 0.00155517384 kg; 1 kg Equals: 643.015 dwt; Common Use: Jewellery, goldsmithing
  • Unit Name: Slug; Symbol: slug; System: US Engineering; Exact Value in kg: 14.593903 kg; 1 kg Equals: 0.068522 slug; Common Use: Engineering dynamics (force/acceleration)
  • Unit Name: Atomic Mass Unit; Symbol: u / Da; System: Physics; Exact Value in kg: 1.66054×10⁻²⁷ kg; 1 kg Equals: 6.022×10²⁶ u; Common Use: Atomic and molecular physics

Construction Material Density Table — Weight per m³ & per ft³ (2026)

Standard densities for construction and civil engineering materials per IS 875 Part 1:1987, BS EN 1991-1-1, and ASCE 7-22. Use these values to estimate dead loads, material quantities, and transport weights.

  • Material: Reinforced Concrete (RCC); Density (kg/m³): 2,500; Density (lb/ft³): 156.1; kg per litre: 2.50; Tonne per m³: 2.50; Notes / Standard: IS 875 P1; BS EN 1991-1-1 Table A.1
  • Material: Plain Concrete (PCC); Density (kg/m³): 2,400; Density (lb/ft³): 149.8; kg per litre: 2.40; Tonne per m³: 2.40; Notes / Standard: IS 875 P1; ACI 318-19
  • Material: Lightweight Concrete (LWC); Density (kg/m³): 1,600–2,000; Density (lb/ft³): 99.8–124.8; kg per litre: 1.60–2.00; Tonne per m³: 1.60–2.00; Notes / Standard: ASTM C330; varies with mix
  • Material: Aerated / AAC Block Concrete; Density (kg/m³): 400–800; Density (lb/ft³): 25.0–50.0; kg per litre: 0.40–0.80; Tonne per m³: 0.40–0.80; Notes / Standard: IS 2185 Part 3; ASTM C869
  • Material: Structural Steel (rolled sections); Density (kg/m³): 7,850; Density (lb/ft³): 489.8; kg per litre: 7.85; Tonne per m³: 7.85; Notes / Standard: IS 2062; BS EN 10025; ASTM A36
  • Material: Cast Iron; Density (kg/m³): 7,150–7,400; Density (lb/ft³): 446.5–462.0; kg per litre: 7.15–7.40; Tonne per m³: 7.15–7.40; Notes / Standard: IS 210; ASTM A48
  • Material: Aluminium (structural alloy); Density (kg/m³): 2,700; Density (lb/ft³): 168.6; kg per litre: 2.70; Tonne per m³: 2.70; Notes / Standard: BS EN 1999-1-1
  • Material: Copper (pure); Density (kg/m³): 8,960; Density (lb/ft³): 559.4; kg per litre: 8.96; Tonne per m³: 8.96; Notes / Standard: ASTM B152
  • Material: Lead (pure); Density (kg/m³): 11,340; Density (lb/ft³): 707.9; kg per litre: 11.34; Tonne per m³: 11.34; Notes / Standard: ASTM B29
  • Material: Stainless Steel (304); Density (kg/m³): 7,900; Density (lb/ft³): 493.3; kg per litre: 7.90; Tonne per m³: 7.90; Notes / Standard: ASTM A240
  • Material: Water (fresh, 4°C); Density (kg/m³): 1,000; Density (lb/ft³): 62.4; kg per litre: 1.00; Tonne per m³: 1.00; Notes / Standard: SI definition
  • Material: Sea Water; Density (kg/m³): 1,025; Density (lb/ft³): 64.0; kg per litre: 1.025; Tonne per m³: 1.025; Notes / Standard: ITTC standard (3.5% salinity)
  • Material: Sand — Dry, loose; Density (kg/m³): 1,450–1,600; Density (lb/ft³): 90.5–99.9; kg per litre: 1.45–1.60; Tonne per m³: 1.45–1.60; Notes / Standard: IS 2116; ASTM C33
  • Material: Sand — Wet, compacted; Density (kg/m³): 1,800–2,000; Density (lb/ft³): 112.4–124.8; kg per litre: 1.80–2.00; Tonne per m³: 1.80–2.00; Notes / Standard: IS 875 Part 1
  • Material: Gravel — Dry (20 mm); Density (kg/m³): 1,500–1,600; Density (lb/ft³): 93.7–99.9; kg per litre: 1.50–1.60; Tonne per m³: 1.50–1.60; Notes / Standard: IS 383:2016
  • Material: Crushed Stone / Granite; Density (kg/m³): 1,650–1,750; Density (lb/ft³): 103.0–109.3; kg per litre: 1.65–1.75; Tonne per m³: 1.65–1.75; Notes / Standard: IS 383:2016; ASTM C33
  • Material: Cement — OPC Loose; Density (kg/m³): 1,400–1,600; Density (lb/ft³): 87.4–99.9; kg per litre: 1.40–1.60; Tonne per m³: 1.40–1.60; Notes / Standard: IS 269; IS 8112
  • Material: Soil — Dry, loose; Density (kg/m³): 1,200–1,600; Density (lb/ft³): 74.9–99.9; kg per litre: 1.20–1.60; Tonne per m³: 1.20–1.60; Notes / Standard: IS 875 Part 1
  • Material: Soil — Compacted (general); Density (kg/m³): 1,700–2,000; Density (lb/ft³): 106.1–124.8; kg per litre: 1.70–2.00; Tonne per m³: 1.70–2.00; Notes / Standard: IS 875 Part 1
  • Material: Clay — Dry; Density (kg/m³): 1,000–1,400; Density (lb/ft³): 62.4–87.4; kg per litre: 1.00–1.40; Tonne per m³: 1.00–1.40; Notes / Standard: IS 875 Part 1
  • Material: Clay — Saturated; Density (kg/m³): 1,600–2,000; Density (lb/ft³): 99.9–124.8; kg per litre: 1.60–2.00; Tonne per m³: 1.60–2.00; Notes / Standard: IS 875 Part 1
  • Material: Asphalt / Bituminous Mix; Density (kg/m³): 1,800–2,300; Density (lb/ft³): 112.4–143.6; kg per litre: 1.80–2.30; Tonne per m³: 1.80–2.30; Notes / Standard: IS 73; ASTM D3515
  • Material: Brick — Common (fired clay); Density (kg/m³): 1,600–1,900; Density (lb/ft³): 99.9–118.7; kg per litre: 1.60–1.90; Tonne per m³: 1.60–1.90; Notes / Standard: IS 1077; BS EN 771-1
  • Material: Brick — Engineering; Density (kg/m³): 2,000–2,200; Density (lb/ft³): 124.8–137.3; kg per litre: 2.00–2.20; Tonne per m³: 2.00–2.20; Notes / Standard: IS 2180
  • Material: Glass (float / structural); Density (kg/m³): 2,500–2,700; Density (lb/ft³): 156.1–168.6; kg per litre: 2.50–2.70; Tonne per m³: 2.50–2.70; Notes / Standard: BS EN 572-1
  • Material: Timber — Softwood (pine, spruce); Density (kg/m³): 400–600; Density (lb/ft³): 25.0–37.5; kg per litre: 0.40–0.60; Tonne per m³: 0.40–0.60; Notes / Standard: IS 399; EN 338
  • Material: Timber — Hardwood (teak, oak); Density (kg/m³): 700–1,000; Density (lb/ft³): 43.7–62.4; kg per litre: 0.70–1.00; Tonne per m³: 0.70–1.00; Notes / Standard: IS 399; EN 338
  • Material: Plywood (structural); Density (kg/m³): 500–700; Density (lb/ft³): 31.2–43.7; kg per litre: 0.50–0.70; Tonne per m³: 0.50–0.70; Notes / Standard: IS 303; BS EN 636
  • Material: Diesel Fuel; Density (kg/m³): 820–860; Density (lb/ft³): 51.2–53.7; kg per litre: 0.82–0.86; Tonne per m³: 0.82–0.86; Notes / Standard: ASTM D975
  • Material: Petrol / Gasoline; Density (kg/m³): 720–780; Density (lb/ft³): 44.9–48.7; kg per litre: 0.72–0.78; Tonne per m³: 0.72–0.78; Notes / Standard: ASTM D4814
  • Material: Air (at 15°C, 1 atm); Density (kg/m³): 1.225; Density (lb/ft³): 0.0765; kg per litre: 0.001225; Tonne per m³: 0.001225; Notes / Standard: ISA Standard Atmosphere

Key Weight Conversion Formulas & Relationships

Mass (kg) = Volume (m³) × Density (kg/m³)

The fundamental relationshipbetween mass, volume, and density is the basis for all material weight estimates. To find mass, multiply volume by density. To find volume from mass, divide mass by density.

kg → Metric Tonnes Divide by 1,000. Example: 2,500 kg ÷ 1,000 = 2.5 t

kg → Pounds (lb) Multiply by 2.20462. Example: 100 kg × 2.20462 = 220.46 lb

lb → kg Multiply by 0.45359. Example: 150 lb × 0.45359 = 68.04 kg

Tonnes → US Short Tons Multiply by 1.10231. Example: 5 t × 1.10231 = 5.512 US tons

oz → grams Multiply by 28.3495. Example: 8 oz × 28.3495 = 226.8 g

Troy oz → grams Multiply by 31.1035. Example: 1 troy oz × 31.1035 = 31.10 g

UK ton → Metric tonne Multiply by 1.01605. Example: 10 UK tons × 1.016 = 10.16 t

US ton → Metric tonne Multiply by 0.90718. Example: 10 US tons × 0.907 = 9.072 t

Volume conversion note:1 m³ = 1,000 litres = 35.315 ft³ = 1.308 yd³ = 61,023.7 in³. Always convert volume to cubic metres before multiplying by density in kg/m³ for consistent results.

Steel Bar & Section Weight Guide Chart — kg per Metre (2026)

Standard weights of steel reinforcement bars (rebar), flat bars, and TMT bars per metre length. Based on IS 1786:2008 (HYSD bars), BS 4449:2005, and ASTM A615. Steel density used: 7,850 kg/m³.

  • Bar Dia. (mm): 6 mm; Cross-Section Area (mm²): 28.27; Weight (kg/m): 0.222; Weight (lb/ft): 0.149; 10m Length (kg): 2.22; 50m Length (kg): 11.10; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 8 mm; Cross-Section Area (mm²): 50.27; Weight (kg/m): 0.395; Weight (lb/ft): 0.265; 10m Length (kg): 3.95; 50m Length (kg): 19.75; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 10 mm; Cross-Section Area (mm²): 78.54; Weight (kg/m): 0.617; Weight (lb/ft): 0.414; 10m Length (kg): 6.17; 50m Length (kg): 30.85; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 12 mm; Cross-Section Area (mm²): 113.10; Weight (kg/m): 0.888; Weight (lb/ft): 0.596; 10m Length (kg): 8.88; 50m Length (kg): 44.40; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 16 mm; Cross-Section Area (mm²): 201.06; Weight (kg/m): 1.579; Weight (lb/ft): 1.060; 10m Length (kg): 15.79; 50m Length (kg): 78.95; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 20 mm; Cross-Section Area (mm²): 314.16; Weight (kg/m): 2.467; Weight (lb/ft): 1.657; 10m Length (kg): 24.67; 50m Length (kg): 123.35; Grade (IS 1786): Fe 415 / Fe 500
  • Bar Dia. (mm): 25 mm; Cross-Section Area (mm²): 490.87; Weight (kg/m): 3.854; Weight (lb/ft): 2.590; 10m Length (kg): 38.54; 50m Length (kg): 192.70; Grade (IS 1786): Fe 500 / Fe 550
  • Bar Dia. (mm): 28 mm; Cross-Section Area (mm²): 615.75; Weight (kg/m): 4.834; Weight (lb/ft): 3.248; 10m Length (kg): 48.34; 50m Length (kg): 241.70; Grade (IS 1786): Fe 500 / Fe 550
  • Bar Dia. (mm): 32 mm; Cross-Section Area (mm²): 804.25; Weight (kg/m): 6.313; Weight (lb/ft): 4.242; 10m Length (kg): 63.13; 50m Length (kg): 315.65; Grade (IS 1786): Fe 500 / Fe 550
  • Bar Dia. (mm): 36 mm; Cross-Section Area (mm²): 1,017.88; Weight (kg/m): 7.990; Weight (lb/ft): 5.371; 10m Length (kg): 79.90; 50m Length (kg): 399.50; Grade (IS 1786): Fe 550 / Fe 600
  • Bar Dia. (mm): 40 mm; Cross-Section Area (mm²): 1,256.64; Weight (kg/m): 9.864; Weight (lb/ft): 6.630; 10m Length (kg): 98.64; 50m Length (kg): 493.20; Grade (IS 1786): Fe 550 / Fe 600
  • Bar Dia. (mm): 50 mm; Cross-Section Area (mm²): 1,963.50; Weight (kg/m): 15.413; Weight (lb/ft): 10.359; 10m Length (kg): 154.13; 50m Length (kg): 770.65; Grade (IS 1786): Fe 550 / Fe 600

ℹ️ Weight per metre = (π/4) × D² × 7.850 ÷ 1,000,000 — where D is bar diameter in mm. The simplified formula used on site is: Weight (kg/m) = D² ÷ 162.2 (where D is in mm). This gives results within 0.1% of the exact estimate.

Worked Examples — Weight Conversion & Material Weight Estimates

Step-by-step solved examples for common weight conversion and material weight problems in construction and engineering.

Example 1: Concrete Slab Weight

Slab dimensions 10m × 6m × 0.15m

Volume 10 × 6 × 0.15 = 9 m³

Material Reinforced Concrete

Density (IS 875) 2,500 kg/m³

Mass in kg 9 × 2,500 = 22,500 kg

22.5 tonnes

Example 2: Steel Beam Weight

Section ISMB 300 beam

Unit weight 44.2 kg/m (IS handbook)

Span length 8 metres

Number of beams 12 beams

Total mass 44.2 × 8 × 12 = 4,243 kg

4.243 tonnes

Example 3: Sand Volume to Weight

Truckload volume 6 m³

Sand condition Dry, loose

Density 1,600 kg/m³

Mass in kg 6 × 1,600 = 9,600 kg

In tonnes 9.6 metric tonnes

9.6 tonnes

Example 4: Unit Conversion Chain

Starting value 500 lb

Convert to kg 500 × 0.453592 = 226.80 kg

Convert to grams 226,796 g

Convert to tonnes 0.22680 t

Convert to stone 500 ÷ 14 = 35.71 stone

226.80 kg

Weight Measurement Systems — Metric, Imperial, Troy & More

SI Metric System

The International System of Units (SI) defines the kilogram (kg) as the base unit of mass, redefined in 2019 in terms of Planck’s constant. Used universally in science, engineering, and trade. The gram, tonne, and milligram are all SI-derived units.

  • Base unit: kilogram (kg)
  • Standard: BIPM SI Brochure 2019
  • Used in: most countries worldwide

Imperial / US Customary System

The pound (lb) and ounce (oz) form the basis of everyday weight measurement in the United States and historically in the UK. The US ton (short ton = 2,000 lb) and UK ton (long ton = 2,240 lb) differ — always clarify which is intended in international trade.

  • Base unit: pound (lb)
  • US ton = 2,000 lb = 907.2 kg
  • UK ton = 2,240 lb = 1,016 kg

Troy Weight System

Troy weight is used exclusively for precious metals — gold, silver, platinum — and gemstones. The troy ounce (31.1035 g) is heavier than the avoirdupois ounce (28.3495 g). Gold prices on world markets are quoted per troy ounce. Always verify which system is being used in commodity trading.

  • Troy ounce = 31.1035 g
  • Troy pound = 12 troy oz = 373.24 g
  • Markets: LBMA, COMEX, MCX

Carat (Gem Weight)

The metric carat (ct) is used exclusively for gemstones and pearls. 1 carat = 0.2 grams exactly. Not to be confused with karat (k), which measures gold purity. A 1-carat diamond weighs 0.2 g (200 mg). Standardised by the 4th General Conference on Weights and Measures (1907).

  • 1 carat = 0.2 g (exact, SI)
  • 1 carat = 200 mg = 0.00643 troy oz
  • Used: diamonds, rubies, sapphires

Quintal, Maund & Tola

Traditional and agricultural weight units still used in South Asian trade. 1 quintal = 100 kg (metric). The maund (man) varied regionally — the standard maund used by the British in India was 37.324 kg. The tola = 11.664 g (one troy ounce in the subcontinental system).

  • 1 quintal = 100 kg
  • 1 maund (standard) = 37.324 kg
  • 1 tola = 11.664 g

Slug & Force-Mass Units

The slug is a unit of mass in the US engineering system where force is measured in pounds-force (lbf). 1 slug = 14.5939 kg (the mass that accelerates at 1 ft/s² when a force of 1 lbf is applied). Used in structural dynamics, fluid mechanics, and aerospace engineering estimates.

  • 1 slug = 14.5939 kg
  • Used: US aerospace and dynamics
  • Rarely used outside specialist engineering

Quick Weight Conversion Reference Cards

Kilograms → Pounds

lb = kg × 2.20462

Example: 75 kg × 2.20462 = 165.35 lb. Reverse: lb ÷ 2.20462 = kg

Kilograms → Metric Tonnes

t = kg ÷ 1,000

Example: 2,500 kg ÷ 1,000 = 2.5 tonnes. Common in concrete and steel estimate.

Pounds → Kilograms

kg = lb × 0.453592

Example: 200 lb × 0.453592 = 90.72 kg. Exact: 1 lb = 0.45359237 kg (SI definition).

US Tons → Metric Tonnes

t = US ton × 0.907185

Example: 10 US tons × 0.907 = 9.072 tonnes. Always clarify US vs UK ton in trade.

UK Long Tons → Metric Tonnes

t = UK ton × 1.01605

Example: 10 UK tons × 1.016 = 10.16 tonnes. UK ton = 2,240 lb = 1,016.05 kg.

Ounces → Grams

g = oz × 28.3495

Example: 16 oz × 28.3495 = 453.59 g (= 1 lb). Used in food, retail, pharmacy.

Troy Ounces → Grams

g = troy oz × 31.1035

Example: 1 troy oz = 31.1035 g. Gold spot price quoted per troy oz globally.

Stone → Kilograms (Body Weight)

kg = stone × 6.35029

Example: 12 stone × 6.350 = 76.20 kg. 1 stone = 14 lb. Used in UK for body weight.

Grams → Milligrams

mg = g × 1,000

Example: 5 g × 1,000 = 5,000 mg. Used in pharmaceuticals and laboratory science.

Weight Conversion Tips — Common Mistakes & Best Practices

Always Clarify “Ton” — US, UK, or Metric

The word “ton” means three different things: US short ton (2,000 lb = 907 kg), UK long ton (2,240 lb = 1,016 kg), and metric tonne (1,000 kg). In international trade and engineering, always write “metric tonne” or “short ton” — never just “ton.” The difference is over 12% between US and metric tonnes.

Mass ≠ Weight (Force) in Engineering

In everyday use, “weight” means mass in kg. In engineering physics, weight is a force measured in Newtons (N) where Weight = Mass × g (9.81 m/s²). So 100 kg has a weight force of 981 N = 100 kgf (kilogram-force). Structural loads use kN (kilonewtons) — always check which system your drawings use.

Wet vs Dry Material Density Matters Significantly

Wet sand weighs approximately 1,900 kg/m³ vs 1,500 kg/m³ dry — a 27% difference. For site quantities, soil swell factors mean the volume you excavate is 20–30% more than you fill back. Cement in a sealed bag is 1,500 kg/m³; once opened and exposed to humidity, bulk density drops to 1,200 kg/m³. Always specify the moisture condition when ordering materials.

Troy Ounce ≠ Avoirdupois Ounce

The troy ounce (31.1035 g) used for gold and silver is 10% heavier than the avoirdupois ounce (28.3495 g) used for everything else. When gold is quoted at £1,200 per ounce, that is per troy ounce. This distinction is critical in precious metals trading — confusing the two leads to significant pricing errors.

Density Varies with Temperature and Moisture

Water density changes from 999.84 kg/m³ at 0°C to 958.4 kg/m³ at 100°C — a 4.3% variation. Soil density changes dramatically with moisture content. Concrete density increases slightly after full curing as hydration products form. For precision estimates (e.g., tank volumes, thermodynamics), use temperature-specific density values rather than nominal figures.

Use Density for Freight & Load Estimates

A standard 20-foot shipping container holds approximately 33 m³ of volume and has a payload limit of about 28 tonnes. Sand at 1,600 kg/m³ would fill the volume limit (53 tonnes) before the weight limit — so only ~17.5 m³ can be loaded. Steel at 7,850 kg/m³ would exceed the weight limit at only 3.6 m³ of volume. Always check both volume and weight limits for freight planning.

Frequently Asked Questions — Weight Conversion & Material Weight

How many kg in a metric tonne?

There are exactly 1,000 kilograms in one metric tonne (also spelled “ton” in some countries). This is the SI definition: 1 metric tonne = 1,000 kg = 1 Mg (megagram). To convert from kg to tonnes, divide by 1,000. To convert from tonnes to kg, multiply by 1,000. Example: 2,500 kg of reinforced concrete = 2.5 metric tonnes.

How many kg in a pound (lb)?

One pound (lb) equals exactly 0.45359237 kilograms — this is the international definition set in 1959 by the international yard and pound agreement. To convert pounds to kg, multiply by 0.453592. To convert kg to pounds, multiply by 2.20462. Example: 100 kg × 2.20462 = 220.46 lb. A person weighing 75 kg weighs 165.35 lb or 11 stone 11.35 lb in UK notation.

What is the difference between a US ton and a UK ton?

A US short ton = 2,000 pounds = 907.185 kg. A UK long ton = 2,240 pounds = 1,016.047 kg. A metric tonne = 1,000 kg = 2,204.62 lb. The UK long ton is approximately 12% heavier than the US short ton. In modern international trade, “tonne” almost always means the metric tonne (1,000 kg). When using “ton” in engineering contracts, always specify which system is being used.

How much does 1 cubic metre of concrete weigh?

One cubic metre of reinforced concrete (RCC) weighs approximately 2,500 kg (2.5 metric tonnes) per IS 875 Part 1 and BS EN 1991-1-1. Plain concrete (PCC, no reinforcement) weighs approximately 2,400 kg/m³. Lightweight concrete weighs 1,600–2,000 kg/m³. Aerated concrete (AAC) weighs only 400–800 kg/m³. The density varies with the mix design, aggregate type, and moisture content.

How much does 1 cubic metre of sand weigh?

One cubic metre of dry, loose sand weighs approximately 1,450–1,600 kg, depending on particle size and shape. Wet or compacted sand weighs 1,800–2,000 kg/m³. River sand typically weighs around 1,600 kg/m³ in dry condition. For purchasing purposes: 1 m³ of sand = approximately 1.6 tonnes (dry). A standard construction truck carrying 6 m³ of sand carries approximately 9.6 tonnes.

What is a troy ounce and how does it differ from a regular ounce?

A troy ounce = 31.1034768 grams, while a regular (avoirdupois) ounce = 28.3495231 grams — so a troy ounce is about 9.7% heavier. Troy weight is used exclusively for precious metals (gold, silver, platinum, palladium) and gemstones. Gold and silver market prices are always quoted per troy ounce. Never confuse the two: if you buy 1 oz of gold, you’re getting a troy ounce, but if you buy 1 oz of butter, that’s an avoirdupois ounce.

How do I estimate the weight of a steel bar or rebar?

Use the formula:Weight (kg/m) = D² ÷ 162.2where D is the bar diameter in millimetres. Example: for a 16 mm bar, weight = 16² ÷ 162.2 = 256 ÷ 162.2 = 1.579 kg per metre. For total weight: multiply kg/m by the length in metres, then by the number of bars. This formula is based on steel density of 7,850 kg/m³ and gives results within 0.1% of the exact estimate.

How many grams in an ounce?

There are approximately 28.3495 grams in one avoirdupois ounce (used for food, everyday goods). There are 31.1035 grams in one troy ounce (used for precious metals). The commonly remembered approximation is “1 oz ≈ 28.35 g” for everyday use. For pharmaceutical work, the apothecary ounce (now largely obsolete) = 31.1035 g, same as troy. Always use the exact value for commercial or scientific purposes: 1 oz (av) = 28.3495231 g exactly.

What is the weight of 1 litre of water?

One litre of pure water weighs exactly 1 kilogram (1,000 grams) at 4°C — this was the original definition of the kilogram. At other temperatures: at 20°C, 1 litre of water weighs 0.9982 kg; at 100°C, 0.9584 kg. Sea water (3.5% salinity) at 15°C weighs 1.025 kg per litre. This relationship (1 L water = 1 kg) is very convenient for practical estimates and is accurate enough for most engineering purposes at normal temperatures.

How do I convert cubic feet to kg for materials like concrete or sand?

First convert cubic feet to cubic metres: 1 ft³ = 0.028317 m³. Then multiply by the material density in kg/m³. Example: 50 ft³ of concrete = 50 × 0.028317 = 1.416 m³. At 2,500 kg/m³: 1.416 × 2,500 = 3,540 kg = 3.54 tonnes. Alternatively, use the density in lb/ft³ directly: concrete weighs about 156 lb/ft³, so 50 ft³ × 156 = 7,800 lb = 3,538 kg. The two methods give the same result.

Weight & Mass Glossary — Key Terms Defined

Mass

The amount of matter in an object, measured in kilograms (kg). Mass does not change with location — it is the same on Earth, the Moon, or in space. This is what a scale measures when you “weigh” something in everyday life.

Weight (Force)

In physics, weight is the gravitational force acting on a mass: W = m × g (where g = 9.81 m/s² on Earth). Measured in Newtons (N) or kilonewtons (kN). 1 kg of mass has a weight of 9.81 N = 1 kgf (kilogram-force).

Kilogram (kg)

The SI base unit of mass. Since 2019, defined by fixing Planck’s constant h = 6.62607015×10⁻³⁴ J·s. Previously defined as the mass of the International Prototype Kilogram (IPK) in Paris.

Metric Tonne (t)

1,000 kilograms. Used in civil engineering, bulk materials trade, and manufacturing. Sometimes called “megagram” (Mg) in formal SI notation. Distinct from the US short ton (907 kg) and UK long ton (1,016 kg).

Pound (lb)

The base unit of mass in the imperial and US customary systems. Defined as exactly 0.45359237 kg since 1959. Abbreviation “lb” comes from the Latin libra pondo (pound by weight).

Avoirdupois System

The everyday weight system used in the US and UK for most goods. Based on the grain: 1 pound = 7,000 grains = 16 ounces. Named from the Old French “aveir de peis” (goods of weight).

Troy System

A weight system used exclusively for precious metals and gemstones. 1 troy pound = 12 troy ounces = 373.24 g (lighter than the avoirdupois pound of 453.59 g). Named after the city of Troyes, France, a major medieval trading centre.

Density (ρ)

Mass per unit volume: ρ = m ÷ V, measured in kg/m³. Determines how heavy a material is for a given volume. Water = 1,000 kg/m³; steel = 7,850 kg/m³; air = 1.225 kg/m³. The ratio of material density to water density is called specific gravity (SG).

Specific Gravity (SG)

The ratio of a material’s density to the density of water (1,000 kg/m³). A dimensionless number. SG of steel = 7.85; concrete = 2.4–2.5; sand aggregate = 2.65. Used extensively in concrete mix design estimates.

Bulk Density

The mass of a loose or granular material per unit of total volume (including air voids between particles). Sand bulk density ≈ 1,500 kg/m³ vs its particle density of 2,650 kg/m³. Used for material ordering and container sizing.

Grain (gr)

The smallest unit in the avoirdupois and troy systems. 1 grain = 0.06479891 grams exactly. Both systems share the same grain. Used for measuring gunpowder, bullets, medication doses, and historically for weighing gold dust.

Newton (N)

The SI unit of force (and therefore weight as a force): 1 N = 1 kg·m/s². The weight force of 1 kg mass on Earth = 9.81 N ≈ 1 kgf. Structural loads in modern codes are expressed in kN (kilonewtons) or kN/m² (kiloPascals).

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