Instantly convert length, area, volume, weight, pressure, temperature, force, speed & energy — metric and imperial, built for engineers, contractors and surveyors.
Construction projects in 2026 span multiple countries, unit systems, and disciplines — from metric structural engineering to imperial site surveys, from SI pressure units to PSI on US equipment datasheets. Having every unit conversion guide in one place saves time, reduces errors, and keeps your estimates consistent across every stage of a project.
This page provides nine fully interactive unit conversion guides covering every measurement type used in construction, civil engineering, and quantity surveying — length, area, volume, weight/mass, pressure, temperature, force, speed, and energy/power. Each conversion guide shows all equivalent values simultaneously so you see the full picture at a glance.
Length
mm, cm, m, km, in, ft, yd, miles
Area
mm², cm², m², ha, in², ft², yd², acres
Volume
m³, ft³, yd³, L, US/UK gal, bbl
Weight
kg, g, t, lb, oz, ton (US/UK)
Pressure
MPa, kPa, PSI, bar, N/mm², kN/m²
Temperature
°C, °F, K — concrete & curing
Force
kN, N, MN, kgf, lbf, kip, tonf
Speed
m/s, km/h, mph, ft/s, knots
Energy
kJ, MJ, kWh, BTU, kcal, ft·lbf
Why Construction Unit Conversion guides Are Essential in 2026
Unit conversion errors are a leading cause of costly mistakes in construction. Having reliable, instant conversion guides for every measurement type protects your project.
International Projects & Supply Chains
UK and European projects use SI metric units; US suppliers, equipment, and specifications use imperial. Structural steel sections, concrete strengths (N/mm² vs PSI), pipe pressures (bar vs PSI), and survey distances (m vs ft) all require constant conversion when working across borders in 2026.
Specification Compliance
BS EN, Eurocode, and ASTM specifications use different unit systems. Checking that imported equipment meets a UK pressure specification (kPa) when its datasheet shows PSI, or verifying a US concrete strength grade against a UK C-class designation, requires fast and accurate unit conversion.
Cost Planning & Procurement
Material prices — steel (£/tonne), concrete (£/m³), earthwork (£/yd³), timber (£/m³) — must be compared across suppliers using different units. Quantity surveyors preparing Bills of Quantities (NRM2) need instant conversion between metric and imperial to cross-check international tender returns. For related background, see Volume Conversion Guide.
Plant and Equipment Selection
Crane lifting capacities (tonnes vs kips), pump pressures (bar vs PSI), generator output (kW vs HP), compressor flow rates (m³/min vs CFM), and vehicle speeds (km/h vs mph) all require unit conversion when selecting plant from mixed international catalogues.
Concrete Temperature Control
Concrete temperature limits (max 30°C at discharge, min 5°C for curing) must be checked against thermometer readings and weather forecasts — which may be in Fahrenheit on US equipment. Cold weather concreting and hot weather management both depend on accurate temperature conversion in real time on site.
Survey and Setting Out
Ordnance Survey coordinates, drawing dimensions, and GPS data may mix metric and imperial units on legacy projects or when working to old drawings. Setting-out engineers converting imperial drawings to metric control points, or vice versa, need immediate and accurate length conversion to avoid positioning errors.
All Unit Conversion guides — 2026
Length Conversion guide
mm · cm · m · km · in · ft · yd · mile · nautical mile
Area Conversion guide
mm² · cm² · m² · ha · km² · in² · ft² · yd² · acre
Volume Conversion guide
m³ · ft³ · yd³ · cm³ · L · mL · US gal · UK gal · bbl
Weight / Mass Conversion guide
kg · g · mg · t · lb · oz · US ton · UK ton · kip
Pressure Conversion guide
MPa · kPa · Pa · N/mm² · bar · PSI · atm · kN/m²
Temperature Conversion guide
°C · °F · K — concrete curing & hot/cold weather
️ Concrete limits:Fresh concrete ≥ 5°C (41°F) · Discharge ≤ 30°C (86°F) · Curing stops below 0°C (32°F)
Force / Load Conversion guide
N · kN · MN · kgf · lbf · kip · tonf (UK) · tonf (US)
Speed Conversion guide
m/s · km/h · mph · ft/s · ft/min · knots
Energy & Power Conversion guide
J · kJ · MJ · kWh · BTU · kcal · ft·lbf · kW · HP
Essential Construction Conversion Reference Tables 2026
Quick-reference factors for the most commonly needed conversions across all measurement types in construction and civil engineering.
Length — Key Conversion Factors
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- From: 1 mm; To mm: 1; To cm: 0.1; To m: 0.001; To inches: 0.03937; To feet: 0.003281; To yards: 0.001094
- From: 1 cm; To mm: 10; To cm: 1; To m: 0.01; To inches: 0.3937; To feet: 0.03281; To yards: 0.01094
- From: 1 m; To mm: 1,000; To cm: 100; To m: 1; To inches: 39.3701; To feet: 3.28084; To yards: 1.09361
- From: 1 km; To mm: 1,000,000; To cm: 100,000; To m: 1,000; To inches: 39,370.1; To feet: 3,280.84; To yards: 1,093.61
- From: 1 inch; To mm: 25.4; To cm: 2.54; To m: 0.0254; To inches: 1; To feet: 0.08333; To yards: 0.02778
- From: 1 foot; To mm: 304.8; To cm: 30.48; To m: 0.3048; To inches: 12; To feet: 1; To yards: 0.33333
- From: 1 yard; To mm: 914.4; To cm: 91.44; To m: 0.9144; To inches: 36; To feet: 3; To yards: 1
- From: 1 mile; To mm: 1,609,344; To cm: 160,934.4; To m: 1,609.344; To inches: 63,360; To feet: 5,280; To yards: 1,760
Pressure — Key Conversion Factors
- From: 1 MPa; MPa: 1; kPa: 1,000; N/mm²: 1; PSI: 145.038; bar: 10; atm: 9.8692; kN/m²: 1,000
- From: 1 kPa; MPa: 0.001; kPa: 1; N/mm²: 0.001; PSI: 0.14504; bar: 0.01; atm: 0.009869; kN/m²: 1
- From: 1 PSI; MPa: 0.006895; kPa: 6.8948; N/mm²: 0.006895; PSI: 1; bar: 0.068948; atm: 0.068046; kN/m²: 6.8948
- From: 1 bar; MPa: 0.1; kPa: 100; N/mm²: 0.1; PSI: 14.5038; bar: 1; atm: 0.98692; kN/m²: 100
- From: 1 atm; MPa: 0.101325; kPa: 101.325; N/mm²: 0.101325; PSI: 14.696; bar: 1.01325; atm: 1; kN/m²: 101.325
- From: 1 kN/m²; MPa: 0.001; kPa: 1; N/mm²: 0.001; PSI: 0.14504; bar: 0.01; atm: 0.009869; kN/m²: 1
Force — Key Conversion Factors
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- From: 1 N; N: 1; kN: 0.001; kgf: 0.10197; lbf: 0.22481; kip: 0.000225; UK tonf: 0.0001004
- From: 1 kN; N: 1,000; kN: 1; kgf: 101.972; lbf: 224.809; kip: 0.22481; UK tonf: 0.10036
- From: 1 MN; N: 1,000,000; kN: 1,000; kgf: 101,972; lbf: 224,809; kip: 224.809; UK tonf: 100.361
- From: 1 kgf; N: 9.80665; kN: 0.009807; kgf: 1; lbf: 2.20462; kip: 0.002205; UK tonf: 0.000984
- From: 1 lbf; N: 4.44822; kN: 0.004448; kgf: 0.45359; lbf: 1; kip: 0.001; UK tonf: 0.000446
- From: 1 kip; N: 4,448.22; kN: 4.44822; kgf: 453.592; lbf: 1,000; kip: 1; UK tonf: 0.44643
- From: 1 UK tonf; N: 9,964.02; kN: 9.96402; kgf: 1,016.05; lbf: 2,240; kip: 2.24; UK tonf: 1
Weight / Mass — Key Conversion Factors
- From: 1 kg; kg: 1; g: 1,000; t (metric): 0.001; lb: 2.20462; oz: 35.274; US ton: 0.001102; UK ton: 0.000984
- From: 1 t (metric); kg: 1,000; g: 1,000,000; t (metric): 1; lb: 2,204.62; oz: 35,274; US ton: 1.10231; UK ton: 0.98421
- From: 1 lb; kg: 0.453592; g: 453.592; t (metric): 0.000454; lb: 1; oz: 16; US ton: 0.0005; UK ton: 0.000446
- From: 1 oz; kg: 0.028350; g: 28.350; t (metric): 0.0000284; lb: 0.0625; oz: 1; US ton: 0.0000313; UK ton: 0.0000279
- From: 1 US ton; kg: 907.185; g: 907,185; t (metric): 0.90718; lb: 2,000; oz: 32,000; US ton: 1; UK ton: 0.892857
- From: 1 UK ton; kg: 1,016.05; g: 1,016,047; t (metric): 1.01605; lb: 2,240; oz: 35,840; US ton: 1.12; UK ton: 1
Pro Tips for Construction Unit Conversion — 2026
Avoid the most common unit conversion mistakes in structural engineering, site management, and procurement.
1 N/mm² = 1 MPa — Always
The units N/mm² (newtons per square millimetre) and MPa (megapascals) are numerically identical. 1 N/mm² = 1 N / (10⁻³m)² = 10⁶ N/m² = 1 MPa. Concrete strength is specified as fck in N/mm² in UK practice and as MPa in Eurocode. These are the same number — no conversion needed.
1 kN/m² = 1 kPa — Also Identical
kN/m² (kilonewtons per square metre) and kPa (kilopascals) are numerically identical. Floor loadings in Eurocode 1 are expressed in kN/m² — the same value in kPa. Pressure gauge readings in kPa from European instruments equal kN/m² — useful for hydraulic and soil pressure estimates.
US Ton ≠ UK Ton ≠ Metric Tonne
Three “tons” — all different. Metric tonne (t) = 1,000 kg. UK long ton = 2,240 lb = 1,016 kg. US short ton = 2,000 lb = 907 kg. Steel prices in UK = £/metric tonne. US crane SWLs often in US short tons. Always specify which ton you mean in international specifications — “1 ton” without a qualifier is ambiguous and has caused serious procurement errors.
Memorise 25.4mm = 1 Inch
The inch-to-millimetre conversion (1 inch = 25.4 mm exactly) is the most used length conversion in construction. From this single fact you can derive: 1 foot = 304.8 mm, 1 yard = 914.4 mm, 1 mile = 1,609.344 m. A 12-inch concrete column = 304.8mm ≈ 305mm. A 4-inch cover = 101.6mm. Knowing 25.4 eliminates all need to memorise other imperial-to-metric length factors. For related background, see Length Conversion Guide.
Temperature: °F = (°C × 1.8) + 32
The temperature formula is the only common unit conversion with an additive constant. Quick reference: 0°C = 32°F (freezing). 5°C = 41°F (minimum concrete cure temp). 20°C = 68°F (standard test temp). 30°C = 86°F (max concrete discharge). 100°C = 212°F (boiling). For approximate mental conversion: double the °C and add 30 (error ~1°F at 20°C).
1 kip = 1,000 lbf — US Structural Standard
The kip (kilopound) = 1,000 lbf is the standard unit for structural loads in US practice. US structural drawings show loads in kips and kip-feet. To convert to metric: 1 kip = 4.448 kN. 1 kip-ft = 1.356 kN·m. When reviewing US structural estimates or procuring US structural components, always convert kips to kN for Eurocode compatibility.
Acres vs Hectares — Land Measurement
1 hectare (ha) = 10,000 m² = 2.471 acres. 1 acre = 4,047 m² = 0.4047 ha. UK planning and land use documents typically use hectares; older legal documents and farm land may still use acres. Site area for planning applications in England is declared in hectares. The floor area ratio (FAR / plot ratio) is estimated from gross site area in hectares.
kW vs HP — Plant and Generator Selection
1 metric horsepower (PS/CV) = 0.7355 kW. 1 US/UK mechanical horsepower (hp) = 0.7457 kW. Generator and engine output in Europe is typically quoted in kW; older plant and US/UK equipment uses HP. For generator sizing: 1 kVA ≈ 0.8 kW (at 0.8 power factor). A 100 kVA generator delivers approximately 80 kW — do not confuse kVA and kW when selecting site power supply.
Frequently Asked Questions — Construction Unit Conversion guides 2026
How do I convert metres to feet and inches?
What is the difference between kPa and PSI, and how do I convert?
kPa (kilopascals) is the SI metric pressure unit; PSI (pounds per square inch) is the imperial unit.1 PSI = 6.8948 kPa. To convert kPa to PSI: divide by 6.8948. To convert PSI to kPa: multiply by 6.8948. Examples: A concrete pump operating at 70 bar = 7,000 kPa = 1,015 PSI. Water mains pressure of 50 PSI = 344.7 kPa = 0.345 MPa. Note: 1 MPa = 1 N/mm² = 1,000 kPa = 145.04 PSI. Use the Pressure Conversion guide above for any combination.
How do I convert m² to ft² for floor area?
How do I convert kN (kilonewtons) to tonnes for crane lifting?
To convert kN to metric tonnes (for comparing with crane SWL):tonnes = kN ÷ 9.80665. To convert tonnes to kN: multiply by 9.80665. Example: A structural beam weighing 3.5 tonnes = 3.5 × 9.80665 =34.3 kN. A crane SWL of 50 tonnes = 50 × 9.80665 =490.3 kN. For US cranes rated in US short tons: 1 US short ton = 2,000 lb = 8,896.4 N = 8.896 kN = 0.9072 metric tonnes. Always confirm which “ton” the crane SWL is expressed in — metric tonne, UK long ton, or US short ton.
What is 1 hectare in square metres, and how many hectares is 1 acre?
1 hectare (ha) =10,000 m²exactly (100m × 100m). 1 km² = 100 hectares. 1 acre = 4,046.86 m² =0.4047 hectares. 1 hectare = 2.4711 acres. For planning applications in England and Wales, site area is declared in hectares to two decimal places. A 5-acre development site = 5 × 0.4047 =2.02 ha. A 10,000 m² industrial unit site =1 ha = 2.47 acres.
How do I convert concrete strength from N/mm² to PSI?
Concrete characteristic compressive strength is expressed in N/mm² (= MPa) in UK/Eurocode practice and in PSI in US (ASTM) practice. To convert:PSI = N/mm² × 145.038. To convert PSI to N/mm²: divide by 145.038. Key reference values: C25/30 concrete (fck = 25 N/mm²) ≈ 3,626 PSI ≈3,500 PSI(ASTM f’c 3500 psi is the nearest US grade). C30/37 (30 N/mm²) ≈ 4,351 PSI. C40/50 (40 N/mm²) ≈ 5,802 PSI ≈ 6,000 PSI (ASTM). Use the Pressure Conversion guide for any strength value.
What is the conversion between kJ and BTU for thermal estimates?
1 BTU (British Thermal Unit) =1.05506 kJ. 1 kJ =0.94782 BTU. 1 kWh = 3,600 kJ = 3,412 BTU. Examples: Heat of hydration of Portland cement ≈ 380–420 kJ/kg = 163–181 BTU/lb. HVAC cooling load: 1 tonne of refrigeration (TR) = 12,000 BTU/hr = 3.517 kW. For building energy performance estimates: 1 kWh = 3,412 BTU = 3.6 MJ. Use the Energy Conversion guide above for any thermal unit conversion.
How do I convert wind speed from m/s to mph for Eurocode wind loading?
To convert m/s to mph: multiply by2.23694. To convert mph to m/s: multiply by0.44704. Eurocode 1 (BS EN 1991-1-4) defines wind actions using fundamental basic wind velocity (vb) in m/s. UK basic wind speed maps use m/s. Weather forecasts may use mph. Example: UK site vb = 26 m/s = 26 × 2.237 =58.2 mph. Beaufort Scale: Force 8 (Gale) = 17.2–20.7 m/s = 38.5–46.3 mph. Use the Speed Conversion guide above for any wind speed conversion.
Disclaimer — Unit Conversion guides 2026
For Reference Purposes Only
All conversion factors used in these resources are based on internationally recognised SI definitions and NIST Special Publication 1038 (current 2026 edition), accurate to at least 6 significant figures. Results are provided for general reference and guidance only. For safety-critical engineering estimates, legal measurement, and regulatory compliance, all unit conversions must be verified independently by a qualified engineer or metrologist using formally approved methods. The authors accept no liability for errors arising from the use of these conversion resources.
Definitions Current as of May 2026
Unit definitions used throughout this page are aligned with the International System of Units (SI, 9th Edition, 2019), the UK Weights and Measures Act 1985 (as amended), and ASTM E380 (US standard practice for use of SI). Temperature conversion formulae are exact per the International Temperature Scale (ITS-90). Always confirm the applicable unit system with your contract documents, national standards, and project specification before finalising any engineering estimate.