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Unit Converters
Free online unit converters for every common measurement. Metric to imperial, imperial to metric, and the stranger conversions (hectares to acres, Kelvin to Fahrenheit, fluid ounces to milliliters) that come up once a year and stop you cold. Every converter handles both directions and shows the conversion formula so you can verify against a textbook.
What you can do here
Length, weight, and temperature
Convert millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles. Switch between grams, kilograms, metric tons, ounces, pounds, and stones. Temperature: Celsius, Fahrenheit, and Kelvin with the formulas shown on every result, because temperature conversion is the one unit math that regularly appears on school and engineering exams.
Volume and capacity
Convert milliliters, liters, cubic meters, fluid ounces, cups, pints, quarts, and gallons. Both U.S. and imperial gallons are supported, which matters because they are different (3.785 liters vs 4.546 liters) and routinely mixed up in recipes and fuel economy figures.
Data, time, and timezones
The Data Storage Converter handles bits, bytes, kilobytes up to petabytes, with both decimal (1000-based) and binary (1024-based) conversions. The two definitions disagree by about 10% at gigabyte scale, which matters when specs don’t match reality. The Time Zone Converter handles all IANA timezones with live current-time display.
Currency and cooking
The Currency Converter uses live rates from a standard API with the last-fetched timestamp displayed. The Cooking Measurement Converter adjusts weight-to-volume conversions based on ingredient density, because a cup of flour is not the same weight as a cup of sugar.
Which gallon is the gallon
U.S. gallon is 3.785 liters. Imperial (UK) gallon is 4.546 liters. A 20% difference. American recipes and fuel economy figures use the U.S. gallon; British and many Commonwealth country sources use the imperial gallon. Our Volume Converter specifies which is which explicitly, and defaults to U.S. units on the U.S. locale. If you are following a British cookbook on an American kitchen scale, check the gallon definition before you scale the recipe.
Frequently asked questions
Why does 1 kilogram not equal 2.2 pounds exactly?
It equals 2.20462 pounds. The 2.2 shortcut is close enough for grocery shopping but wrong for precision work like medication dosing or shipping tolerance. Our converter uses the full conversion factor.
Are the temperature formulas the same as my textbook?
Yes. C to F is (C × 9/5) + 32. F to C is (F – 32) × 5/9. K to C is K – 273.15. These are the same formulas used in physics, chemistry, and engineering everywhere.