Volume converter

Convert to liters, then to the target unit. Five US gallons to liters: 5 × 3.785411784 = 18.93 L. Metric volumes nest neatly: 1 L = 1,000 mL = 1,000 cm³, and 1,000 L is one cubic meter. A milliliter and a cubic centimeter, the “cc” of engine sizes and syringes, are the same volume.

Because the US kept an older English wine gallon of 231 cubic inches, while Britain replaced its gallons in 1824 with the imperial gallon, defined today as exactly 4.54609 L. The imperial gallon is about 20% larger, and the gap runs through every smaller unit: a US pint is 473 mL, a British pint 568 mL. The fluid ounces differ too, in the other direction — the US fluid ounce is 29.57 mL and the imperial one 28.41 mL — which is why a British pint holds 20 fluid ounces and an American pint only 16.

It depends on the recipe’s country. A US customary cup is 236.6 mL; the metric cup used in Australia, Canada and New Zealand is 250 mL; and US nutrition labels round the cup to 240 mL under FDA labeling rules. For most cooking the 6% spread does not matter. For baking, where flour and liquid have to balance, it can — and the most reliable fix is a kitchen scale.

Not between 1901 and 1964. In that period the liter was defined as the volume of one kilogram of pure water at its maximum density, which turned out to be 1.000028 dm³ — 28 parts per million too large. The 12th General Conference on Weights and Measures set the liter back to exactly one cubic decimeter in 1964. The most used volume conversions here are gallons to liters and fluid ounces to mL.