Why "UK" is in the name
A UK (Imperial) gallon is not the same size as a US gallon — the UK gallon is about 20% larger (4.54609 liters versus 3.785 liters). The gap runs through every unit derived from it: a UK fluid ounce divides the gallon into 160 parts, while a US fluid ounce divides it into 128, so even though both are called "fluid ounce," they aren't the same volume either. This converter uses the UK Imperial definitions throughout. If you're converting a US recipe or US-specified capacity, use the US Volume Converter instead — the numbers here won't match, and that's expected.
A tablespoon nuance worth knowing
Modern UK recipes, the NHS, and the British Pharmacopoeia all define a teaspoon as exactly 5 mL and a tablespoon as exactly 15 mL — a clean metric standard adopted during the UK's metrication, and what this converter uses. This is different from the older, historical Imperial definition, which derived the tablespoon and teaspoon from the Imperial fluid ounce (working out to roughly 14.2 mL and 3.55 mL respectively) — a definition virtually no current UK recipe actually uses, but one you may still encounter in older cookbooks or reference material. If a very old British recipe's measurements seem slightly off using this converter, that historical/modern split is very likely why.
Exact conversion factors
| Unit | Equal to |
|---|---|
| 1 cubic meter (m³) | 1,000 liters |
| 1 cubic centimeter (cm³) | 1 milliliter (exactly) |
| 1 liter | 1,000 milliliters |
| 1 gallon (UK) | 4.54609 liters (exactly) |
| 1 quart (UK) | ¼ gallon — 1.1365225 liters |
| 1 pint (UK) | ⅛ gallon — 0.56826125 liters |
| 1 fluid ounce (UK) | ⅓₁₆₀ gallon — 28.4130625 mL |
| 1 tablespoon (UK, modern) | 15 mL exactly |
| 1 teaspoon (UK, modern) | 5 mL exactly |
| 1 cubic foot | 1,728 cubic inches (12³) |
Frequently asked questions
How many liters are in a UK gallon?
Exactly 4.54609 liters.
Is a UK gallon bigger than a US gallon?
Yes — about 20% bigger (4.54609 liters versus 3.785411784 liters for a US gallon).
How many fluid ounces are in a UK gallon?
160 — unlike a US gallon, which divides into 128 fluid ounces.