Length, weight, temperature, volume, speed — all the conversions you actually need.
Every unit in a category is stored as a multiple of one base unit, so any pair converts through the base. Temperature is the exception and uses formulas.
One inch is exactly 2.54 centimeters. Six feet is 72 inches, and 72 × 2.54 is 182.88 centimeters. Exact by definition, not by rounding.
The volume case is the one that catches people. A US gallon is about 3.785 liters, while an imperial gallon is about 4.546 liters — a difference of roughly 20%. A British recipe that calls for a gallon is calling for a fifth more liquid than the same word means in a US cookbook.
Temperature is a formula: 350°F is (350 − 32) × 5/9, which is 176.7°C. That is the same number the oven converter rounds onto a gas mark, and rounding a temperature is a decision about baking, not a conversion error.
Conversion factors are exact where the units are defined against each other, and the display is rounded for readability. If you need more digits, the underlying value is more precise than what you see, but a result shown to two decimals should not be quoted to five.
Volume units here are US customary. That covers gallons, quarts, pints, cups, fluid ounces, tablespoons, and teaspoons as an American kitchen uses them. A metric cup, an Australian tablespoon, and an imperial pint are all different sizes, and none of them are in this list.
Mass and weight are treated as interchangeable in everyday use, which they are for anything you would weigh in a kitchen or a suitcase. Strictly, kilograms measure mass and pounds measure force, and the distinction only matters in physics or in very precise trade.
For cooking, remember that volume measures of dry ingredients are approximations by nature. A cup of flour depends on whether it was scooped or spooned, which is why a scale in grams beats any converter for baking.
No. A US gallon is about 3.785 liters and an imperial gallon about 4.546 liters. This converter uses US units throughout.
It should not be, beyond display rounding. The factor is exact. If a value looks wrong, check that you did not switch category and leave the units mismatched.
Use the temperature category or the dedicated oven converter. Fahrenheit to Celsius is (F − 32) × 5/9. Gas marks are a separate scale with fixed stops, so they are approximate at the edges.
Mass is the amount of matter; weight is the force gravity exerts on it. In everyday use the words are interchangeable, and this converter treats them that way.
Yes. A US tablespoon is three US teaspoons. An Australian tablespoon is four teaspoons, which is worth knowing before following a recipe from an Australian book.
No. Volume to weight requires the density of the specific ingredient, so a cup of flour and a cup of sugar weigh different amounts. Use a cooking-specific tool or a scale for that.
Exact conversion factors are NIST's business, and this page rounds the display.
Last updated: November 2, 2026. Reviewed by David Liu. US customary volume units. Display values are rounded.