The UK uses a confusing hybrid of metric and imperial units. Distances on road signs are in miles. Petrol is sold in litres. Beer is served in pints. Body weight is in stones. Temperatures are in Celsius (mostly). Recipes might use grams or ounces. Navigating this everyday mix — let alone understanding American recipes or US product specs — requires confident unit conversion skills. This guide gives you the key conversion factors, quick mental maths tricks, and a reference table for every common situation.
Length and Distance
| From | To | Multiply by | Example |
|---|---|---|---|
| kilometres | miles | 0.6214 | 10 km = 6.21 miles |
| miles | kilometres | 1.6093 | 10 miles = 16.09 km |
| metres | feet | 3.2808 | 1 m = 3.28 ft |
| feet | metres | 0.3048 | 6 ft = 1.83 m |
| centimetres | inches | 0.3937 | 30 cm = 11.81 in |
| inches | centimetres | 2.5400 | 12 in = 30.48 cm |
Quick trick for km to miles: Multiply by 0.6 (not exact but good estimate). 100 km ≈ 62 miles.
Better trick: The Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89...) gives remarkably accurate km-to-miles pairs: 5 km ≈ 3 miles, 8 km ≈ 5 miles, 13 km ≈ 8 miles, 21 km ≈ 13 miles. This works because the ratio of consecutive Fibonacci numbers approaches the golden ratio (1.618) which is close to the km/mile ratio (1.609).
Weight and Mass
| From | To | Multiply by |
|---|---|---|
| kilograms | pounds (lbs) | 2.2046 |
| pounds | kilograms | 0.4536 |
| kilograms | stones | 0.1575 |
| stones | kilograms | 6.3503 |
| grams | ounces (oz) | 0.03527 |
| ounces | grams | 28.35 |
| tonnes (metric) | tons (imperial) | 0.9842 |
Stone-to-kg mental maths: 1 stone = 6.35 kg. So 10 stone = 63.5 kg, 11 stone = 70 kg (approx), 12 stone = 76 kg, 13 stone = 82.5 kg, 14 stone = 89 kg.
Pounds to kg quick method: Divide by 2, then subtract 10%. 150 lbs ÷ 2 = 75, × 0.9 = 68 kg (actual: 68.0 kg — excellent).
volume-and-capacity">Volume and Capacity
| From | To | Multiply by |
|---|---|---|
| litres | UK pints | 1.7598 |
| UK pints | litres | 0.5683 |
| litres | US gallons | 0.2642 |
| litres | UK gallons | 0.2200 |
| millilitres | fluid oz (UK) | 0.03520 |
| fluid oz (UK) | millilitres | 28.41 |
| US fluid oz | millilitres | 29.57 |
| cups (US) | millilitres | 236.6 |
US recipe conversions: 1 US cup = 237 ml | 1 tablespoon = 15 ml | 1 teaspoon = 5 ml
Key difference: UK and US fluid ounces are slightly different (UK fl oz = 28.41 ml; US fl oz = 29.57 ml). For most cooking purposes, treat them as equal, but for precision work, use ml.
Temperature
Celsius to Fahrenheit: °F = (°C × 9/5) + 32
Fahrenheit to Celsius: °C = (°F − 32) × 5/9
Key reference points:
| °C | °F | Context |
|---|---|---|
| -40 | -40 | The one temperature equal in both scales |
| 0 | 32 | Water freezes |
| 20 | 68 | Room temperature |
| 37 | 98.6 | Normal body temperature |
| 100 | 212 | Water boils |
| 180 | 356 | Fan oven for roasting |
Mental maths trick: Double the Celsius, subtract 10%, add 32. 20°C → 40 − 4 + 32 = 68°F ✓ | 25°C → 50 − 5 + 32 = 77°F ✓
Area
| From | To | Multiply by |
|---|---|---|
| m² | sq ft | 10.764 |
| sq ft | m² | 0.0929 |
| hectares | acres | 2.4711 |
| acres | hectares | 0.4047 |
| km² | sq miles | 0.3861 |
Pressure
- 1 bar = 14.504 PSI (tyre pressure: 32 PSI ≈ 2.2 bar)
- 1 atmosphere = 101.325 kPa = 14.696 PSI
Summary
Key quick conversions to memorise: 1 mile = 1.609 km | 1 kg = 2.2 lbs = 0.157 stone | 1 litre = 1.76 UK pints | °F = (°C × 1.8) + 32. Use the Fibonacci sequence for km-to-miles mental arithmetic. For US recipes, 1 cup = 240 ml. Our unit converter handles all categories instantly with full precision.