UK vs US Measurements: A Traveller's Guide
Navigate the confusing differences between UK and US measurements for gallons, pints, clothing sizes, and more.
The UK and US share a language but not always a measurement system. While both use "imperial" units, they're often different imperials. This guide helps travelers and expats navigate the confusing differences.
Distance: Mostly the Same
Good news: miles, yards, feet, and inches are identical in both countries.
- 1 mile = 1.609 km (both countries)
- 1 yard = 3 feet = 36 inches (both countries)
Both countries use miles for road signs and vehicle speed. The UK went metric in 1965 but roads stayed imperial — you'll see miles on motorways and metres on newer signs for short distances.
Volume: Here's Where It Gets Confusing
Gallons:
- US gallon = 3.785 litres = 128 US fluid ounces
- UK gallon = 4.546 litres = 160 UK fluid ounces
A UK gallon is about 20% larger! This matters for:
- Fuel economy: US "miles per gallon" figures look worse because US gallons are smaller. A US car rated at 30 mpg would be 36 mpg in UK gallons.
- Recipes: Always check which gallon a recipe uses.
Pints:
- US pint = 473 mL (16 US fluid ounces)
- UK pint = 568 mL (20 UK fluid ounces)
British pints are 20% larger — which is why British beer glasses look different and Brits feel cheated by American "pints."
Fluid ounces:
- US fluid ounce = 29.57 mL
- UK fluid ounce = 28.41 mL
Counterintuitively, UK fluid ounces are smaller, but there are more of them in UK pints and gallons.
Weight: Body Weight Differences
Pounds and ounces are the same, but usage differs:
- US: Body weight in pounds (e.g., "I weigh 180 pounds")
- UK: Body weight in stones and pounds (e.g., "I weigh 12 stone 12")
1 stone = 14 pounds. To convert: divide pounds by 14 for stones, remainder is pounds.
Example: 180 lbs = 12 stone 12 lbs (180 ÷ 14 = 12 remainder 12)
Cooking Measurements
Cups:
- US cup = 236.6 mL (8 US fluid ounces)
- UK cup = 284 mL (rarely used — most UK recipes use grams)
Tablespoons:
- US tablespoon = 14.8 mL
- UK tablespoon = 15 mL (Australian = 20 mL)
General rule: US recipes use cups and tablespoons; UK recipes typically use grams and millilitres.
Clothing Sizes
Neither country uses metric for clothes, but sizes differ:
Women's clothing:
- US 6 = UK 10
- US 8 = UK 12
- US 10 = UK 14
- (UK size = US size + 4)
Women's shoes:
- US 7 = UK 5
- US 8 = UK 6
- (UK size = US size − 2)
Men's clothing: Generally similar (S, M, L, XL are universal)
Men's shoes:
- US 9 = UK 8
- US 10 = UK 9
- (UK size = US size − 0.5 to 1)
Temperature
Both countries use Fahrenheit historically, but:
- UK: Now officially Celsius for weather, though older Brits often think in Fahrenheit
- US: Fahrenheit for everything everyday
Oven temperatures: UK recipes usually give Celsius with Gas Mark; US recipes give Fahrenheit.
Practical Tips for Travelers
- Fuel: UK sells fuel in litres but measures economy in mpg. Do the conversion before comparing cars.
- Recipes: Check the recipe source. US cups are smaller than UK cups.
- Clothes shopping: Remember the size offset before buying.
- Ordering beer: A UK pint is more generous than a US pint.
- Weather apps: Set to the local unit preference to understand forecasts.