Volume Converter

Cooking is where volume conversion goes wrong most often, because the everyday units people assume are universal genuinely differ by country. A recipe that behaves oddly when followed carefully is frequently a units problem rather than a technique problem.

The cup and the tablespoon both vary

A US customary cup is close to 240 milliliters, while a metric cup used across much of the Commonwealth is 250, and a Japanese cup is 200. Across a recipe calling for several cups, that spread is easily enough to change a batter's consistency.

The tablespoon is the sharper trap because the gap is proportionally larger. Most places treat a tablespoon as roughly 15 milliliters, but the Australian tablespoon is 20, a third larger. In a recipe using several tablespoons of a strong ingredient such as baking powder or salt, that difference is the difference between working and inedible.

Dry and liquid measures are different units

In the US customary system, a dry pint and a liquid pint aren't the same volume, and the same applies to quarts. Dry measures were standardized separately for goods sold by bulk such as grain and produce. Anyone converting agricultural or bulk quantities needs to know which family a figure came from, since the names give no clue.

A related point worth keeping straight: converting a volume to a weight requires knowing the density of the substance, and the two aren't interchangeable. A cup of flour and a cup of honey occupy the same volume and weigh very different amounts, which is why baking recipes that specify grams are more reliable than those specifying cups.

Volume grows with the cube of length

This is the intuition people most often lack. Doubling every dimension of a container multiplies its capacity by eight, not by two, because volume scales with the cube of linear size. A tank twice as tall, twice as wide and twice as deep holds eight times as much.

The same relationship explains why a modest increase in a pan's dimensions changes baking times noticeably, and why scaling a recipe by container size rather than by stated quantity goes wrong quickly. It's also why a liter, defined as a cubic decimeter, connects cleanly to length units while gallons and pints don't.