Unit Converter

How to use the unit converter

1. Choose a category: length, mass, volume, temperature, area, speed, time, data size or energy.
2. Type the value, then pick the unit to convert from and the unit to convert to. The result updates as you type.
3. Use Swap to reverse the direction, and the precision menu to show more or fewer significant digits.
4. Check the table to see the same value in every unit of the category. Use Copy result to copy the answer.

Exact definitions, not rounded factors

Every unit is tied to an exact definition, and conversions are done with exact fractions, not floating point numbers. That is why 1 inch gives exactly 25.4 millimeters and 1 mile gives exactly 1.609344 kilometers. Key definitions used:

• Length: 1 inch = 25.4 mm, 1 foot = 0.3048 m, 1 yard = 0.9144 m, 1 mile = 1,609.344 m, 1 nautical mile = 1,852 m.
• Mass: 1 pound = 0.45359237 kg, 1 ounce = 1/16 pound, 1 stone = 14 pounds, 1 US ton = 2,000 pounds.
• Volume: 1 US gallon = 3.785411784 L, 1 US fluid ounce = 29.5735295625 mL, 1 cup = 8 fl oz, 1 tablespoon = 0.5 fl oz, 1 imperial gallon = 4.54609 L.
• Area: 1 acre = 4,046.8564224 m², 1 hectare = 10,000 m².
• Energy: 1 cal = 4.184 J, 1 kWh = 3,600,000 J, 1 BTU (International Table) = 1,055.05585262 J.

Temperature

Temperature scales have different zero points, so they use formulas rather than a single factor. 100 degrees Celsius is 212 Fahrenheit, 0 Celsius is 273.15 kelvin and -40 is the same on both Celsius and Fahrenheit. Values below absolute zero, which is -273.15 Celsius, -459.67 Fahrenheit or 0 kelvin, are rejected with a message.

Megabytes and mebibytes

Data units come in two families, and the tool labels them clearly. Decimal units (kB, MB, GB, TB) use powers of 1,000. Binary units (KiB, MiB, GiB, TiB) use powers of 1,024. So 1 MB is 1,000,000 bytes, 1 MiB is 1,048,576 bytes, and 1 MB equals 0.95367431640625 MiB. That difference is why a drive sold as 500 GB shows less space in an operating system that counts in binary units.

Precision, limits and privacy

The precision menu sets significant digits from 4 to 15, with trailing zeros removed, and very large or small results use exponent notation. The year is 365.25 days and months are not offered because their length varies. Values are processed in your browser and are never uploaded. For area shapes see the area calculator, and for running speeds use the pace calculator.

Assumptions and limits

• Gallons, cups, ounces and tons are the US customary units unless the unit says imperial. Weight units are treated as mass, as on a kitchen or postal scale.
• The year is a Julian year of 365.25 days.
• Calories are thermochemical, so the food Calorie (kcal) is exactly 4,184 joules.
• Only plain numbers are accepted, with digits and one decimal point. Exponent notation is not entered but can be shown in results.
• Conversions are exact rational arithmetic, so only the displayed result is rounded.

Formulas reviewed October 10, 2026. See the calculation methodology for how SumPanda rounds, tests and sources its formulas.

Frequently asked questions