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Convert liters, gallons, cups, and fluid ounces for recipes and more.
Convert volumes between liters, milliliters, US gallons, fluid ounces, and cups. Perfect for recipes, fuel, and lab work — using the US customary definitions cooks actually use.
Volume conversion is haunted by the gallon problem: the U.S. gallon (3.785411784 liters) and the imperial gallon (4.54609 liters) share a name but differ by 20 percent. The same split infects fluid ounces (29.5735 mL U.S. versus 28.4131 mL imperial), pints, and quarts. The metric side is mercifully simple — milliliters, liters, and cubic meters, all decimal — and it is the legal standard for fuel, beverages, and medicine in nearly every country. In the kitchen, U.S. cooks also juggle teaspoons (4.9289 mL), tablespoons (14.7868 mL), and cups (236.588 mL), none of which match their imperial namesakes exactly.
Exact factors worth knowing: 1 US gallon = 3.785411784 L; 1 imperial gallon = 4.54609 L; 1 US fluid ounce = 29.5735295625 mL; 1 liter = 0.264172 US gallons = 1.75975 imperial pints; 1 cubic meter = 1,000 liters = 264.172 US gallons. Note that dry volumes (bushels, pecks) are a separate system from liquid volumes — a conversion between them is meaningless without knowing the substance.
The highest-stakes volume conversions are fuel economy comparisons (a car's '40 mpg' means different fuel burn in the U.S. versus the UK because the gallons differ), medication dosing (always metric — milliliters, never teaspoons from the cutlery drawer), and aquariums and pools, where a 20 percent gallon error means a 20 percent chemical-dosing error. When a recipe or manual says 'gallon' without qualification, check its country of origin before converting.
Every unit converts through liters with its exact factor: 1 US gallon = 3.785411784 L, 1 US fluid ounce = 0.0295735295625 L, 1 US cup = 0.2365882365 L. The result is value × factor[from] ÷ factor[to].
Multiply by 3.785411784: 10 x 3.785411784 = 37.854, rounded to 37.85 L. A car with a 10-gallon tank therefore holds about 37.9 liters — useful when comparing against European tank sizes quoted in liters. The imperial trap: 10 imperial gallons would be 45.46 L, a full 20 percent more, which is why a British car advertised at '50 mpg' is not directly comparable to an American car at '50 mpg.' Reverse: 40 liters / 3.785411784 = 10.567 US gallons.
Divide by 29.5735295625 mL per fl oz: 500 / 29.5735295625 = 16.907, rounded to 16.9 fl oz. So the standard half-liter bottle is just under 17 US fluid ounces — the '16.9 oz' label on American bottles is exactly this. In imperial ounces it would be 500 / 28.4130625 = 17.6 fl oz, a small but real difference that matters in precise recipes. For quick kitchen math, 250 mL is about 1 US cup (236.6 mL), close enough for most cooking.
3.78541 liters. Enter 1, choose gal → L — the US liquid gallon is exactly 3.785411784 liters.
8 fluid ounces. Enter 1, choose cup → fl oz — a US cup is defined as 8 US fluid ounces.
This uses US customary units (the ones in American recipes and fuel pumps). An imperial gallon is larger — 4.54609 liters.