Imperial Measurements Explained
Last updated February 14, 2026 · Volume
The United Kingdom is officially metric, but a defined set of Imperial units remains in legal and everyday use. Understanding which ones survive — and how they differ from their American namesakes — avoids most conversion mistakes.
Imperial units still in daily UK use
- Miles and miles per hour on all road signs
- Pints for draught beer, cider and doorstep milk (568 mL, not the 473 mL US pint)
- Stone and pounds for body weight
- Feet and inches for human height
- Acres for farmland alongside hectares
Where Imperial differs from US customary
| Unit | Imperial vs US |
|---|---|
| Gallon | 4.54609 L vs 3.785411784 L |
| Pint | 568.261 mL vs 473.176 mL |
| Fluid ounce | 28.4131 mL vs 29.5735 mL |
| Ton | 2,240 lb vs 2,000 lb |
| Inch, foot, mile | Identical in both systems |
Spelling
UK, Canadian, Australian and New Zealand English use metre, litre and kilometre; US English uses meter, liter and kilometer. The units are identical — only the spelling differs.