Imperial/Metric Converter
Comprehensive conversion between Imperial and Metric measurement systems. Convert length, area, volume, weight, temperature, and pressure units commonly used in construction.
Why Both Systems Matter
While the UK officially uses the metric system, Imperial measurements are still widely used in construction. Timber is sold as "4×2", sheet materials as "8×4", and many tradespeople still think in feet and inches. This converter bridges both systems.
Quick Reference Tables
Length Conversions
| Metric | Imperial |
|---|---|
| 1 mm | 0.039 in |
| 25.4 mm | 1 inch |
| 304.8 mm | 1 foot |
| 1 metre | 3.281 ft / 1.094 yd |
| 1 km | 0.621 miles |
Area Conversions
| Metric | Imperial |
|---|---|
| 1 cm² | 0.155 in² |
| 1 m² | 10.764 ft² |
| 1 hectare | 2.471 acres |
| 1 km² | 247.1 acres |
Volume Conversions
| Metric | Imperial |
|---|---|
| 1 ml | 0.035 fl oz |
| 1 litre | 1.76 pints / 0.22 gallons |
| 1 m³ | 35.315 ft³ / 1.308 yd³ |
| 4.546 litres | 1 UK gallon |
Weight Conversions
| Metric | Imperial |
|---|---|
| 1 gram | 0.035 oz |
| 28.35 grams | 1 ounce |
| 1 kg | 2.205 lb |
| 6.35 kg | 1 stone |
| 1 tonne | 0.984 long tons |
Temperature Conversions
°C = (°F - 32) × 5/9
°F = (°C × 9/5) + 32
K = °C + 273.15
| Celsius | Fahrenheit | Context |
|---|---|---|
| -10°C | 14°F | Cold winter day |
| 0°C | 32°F | Water freezes |
| 20°C | 68°F | Room temperature |
| 100°C | 212°F | Water boils |
Construction-Specific Conversions
- 4×2 timber: 100mm × 50mm
- 8×4 sheet: 2440mm × 1220mm
- 1 yard concrete: 0.765 m³
- 1 ton (UK): 1016 kg (long ton)
- 1 ton (US): 907 kg (short ton)
- 1 bar: 14.5 psi
TXTexas IBC / IRC (AHJ amendments)
References & Sources
Standards Cited
- NIST Special Publication 811 — Guide for the Use of the International System of Units (SI)
Authoritative source for all imperial-to-metric conversion factors used in this calculator View → - ASTM E621 — ASTM E621 — Standard Practice for the Use of Metric (SI) Units in Building Design and Construction
Provides guidance on metric conversions for North American construction applications - NIST Handbook 44 — Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices
Legal definitions of US customary units and their metric equivalents View →
Formulas Used
- Generic Unit Conversion:
result = value x (fromFactor / toFactor)
Source: NIST SP 811 — All conversions route through an SI base unit (metres, kilograms, etc.) - Celsius to Fahrenheit:
F = (C x 9/5) + 32
Source: NIST SP 811 - Fahrenheit to Celsius:
C = (F - 32) x 5/9
Source: NIST SP 811 - Celsius to Kelvin:
K = C + 273.15
Source: SI Brochure
Key Assumptions
- 1 inch = 0.0254 m exactly — NIST Special Publication 811
- 1 US gallon = 0.00378541 m³ (3.78541 litres) — NIST Special Publication 811
- 1 US short ton = 907.185 kg — NIST Special Publication 811
- 1 US hundredweight = 45.3592 kg (100 lb) — NIST Special Publication 811
- Pressure conversion: 1 psi = 6894.76 Pa — NIST Special Publication 811