How this works
Pick a unit, type a value, and see the equivalent in every other common volume unit at once. The metric side covers millilitres up to cubic metres; the US imperial side covers cooking measures (teaspoons, tablespoons, cups) and the larger fluid units (fluid ounces through gallons). UK gallons are included separately because they're ~20% bigger than US gallons — a common source of confusion when reading recipes or fuel-economy figures across the Atlantic.
The formula
Key factors: 1 mL = 0.001 L, 1 m³ = 1000 L, 1 US gal = 3.785411784 L (exact, from 231 in³), 1 UK gal = 4.54609 L (exact). Cooking units derive from US fl oz: 1 cup = 8 fl oz, 1 tbsp = 1/2 fl oz, 1 tsp = 1/6 fl oz. Every conversion routes through litres, so rounding never compounds across hops.
Example calculation
- 1 L = 33.81 fl oz (US) ≈ 4.23 cups (US)
- 1 US gallon = 3.785 L. 1 UK gallon = 4.546 L (~20% more).
- 1 cup (US) = 236.6 mL — handy for converting US recipes to grams via density.
- 1 tsp = 4.93 mL, 1 tbsp = 14.79 mL — note these are US measures.
Frequently asked questions
Why is a UK gallon different from a US gallon?
They're different historical definitions. The US gallon (3.785 L) descends from the 1707 English wine gallon — a measure of 231 cubic inches. The UK abandoned that in 1824 and standardised on the imperial gallon (4.546 L), defined as 10 lb of water at a specific temperature. The US kept the older definition. Result: a "gallon" of milk, fuel, or paint in London is ~20% bigger than the same word in New York.
How many grams in a cup of flour?
Volume → mass conversions need the density of the substance. A US cup is 236.6 mL, but the mass it holds depends on what's in it: water ≈ 236.6 g (density 1), all-purpose flour ≈ 125 g (loose), granulated sugar ≈ 200 g, butter ≈ 227 g. This calculator only handles volume → volume; for cup-to-grams use a recipe-specific lookup since density varies by ingredient.
Are tsp and tbsp the same in the UK and US?
Almost. US: 1 tsp = 4.929 mL, 1 tbsp = 14.787 mL. UK: 1 tsp = 5 mL exactly, 1 tbsp = 15 mL exactly (since 1991 metric standardisation). The ~1.4% gap is small enough not to matter for most cooking but can matter for precise baking or chemistry. This calculator uses US values; for UK precision round US tsp/tbsp up slightly.