How volume conversion works
To convert between any pair of volume units, the simplest approach is to use the liter as an intermediate step. The input value is first turned into liters, and that total is then converted into the desired target unit. That is exactly how this calculator works behind the scenes.
Conversion factors used
1 liter = 1,000 milliliters
1 cubic meter = 1,000 liters
1 US gallon = 3.785411784 liters (exact definition)
1 US quart = 0.946352946 liters (one quarter of a gallon)
1 US fluid ounce = 29.5735295625 milliliters
Worked example
A US gallon of gasoline equals roughly 3.79 liters, since 1 multiplied by 3.785411784 gives that value. In milliliters, the same 3.79 liters correspond to 3,785.41 mL, since each liter is exactly 1,000 milliliters.
US gallon versus imperial gallon
It is common to confuse the US gallon, used in the United States, with the British imperial gallon, used in the United Kingdom and part of the Commonwealth. The US gallon is about 3.785 liters, while the imperial gallon is about 4.546 liters, nearly 20% more. This calculator works with the US gallon, the one most commonly used in technical content and recipes.
Converting cooking measurements to milliliters
Recipes often use cups, tablespoons and teaspoons as units of measurement, but these do not have an officially standardized size, they vary depending on the kitchen tool being used. In everyday cooking practice, the most widely accepted values are 240 mL for a cup, 15 mL for a tablespoon, and 5 mL for a teaspoon. The calculator on this page uses those rounded values to convert any amount of these measurements into milliliters and liters.