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
UKUK Building Regulations
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 → - Weights and Measures Act 1985 — UK Weights and Measures Act 1985
Legal definitions of UK imperial units (stone, hundredweight, long ton, UK gallon, pint) and their metric equivalents
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 UK gallon = 0.00454609 m³ (4.54609 litres) — Weights and Measures Act 1985
- 1 UK long ton = 1016.05 kg — Weights and Measures Act 1985
- 1 US gallon = 0.00378541 m³ (3.78541 litres) — NIST Special Publication 811
- 1 stone = 6.35029 kg (UK imperial) — Weights and Measures Act 1985
- Pressure conversion: 1 psi = 6894.76 Pa — NIST Special Publication 811