Unit converters
Convert between metric, imperial and US units — and see every unit at once.
Length Converter
Convert inches, feet, miles, centimeters, meters and more — all units at once.
Weight Converter
Convert pounds, kilograms, ounces, grams, stone and tons instantly.
Temperature Converter
Convert between Fahrenheit, Celsius, Kelvin and Rankine with exact formulas.
Volume Converter
Convert cups, spoons, fluid ounces, gallons, liters and milliliters — US and UK.
Area Converter
Convert square feet, square meters, acres and hectares for rooms, homes and land.
Speed Converter
Convert mph, km/h, knots, meters per second and feet per second.
Data Storage Converter
Convert bytes, KB, MB, GB, TB and binary MiB/GiB/TiB units.
Time Unit Converter
Convert seconds, minutes, hours, days, weeks, months and years.
Currency Converter
Convert between 160+ world currencies using daily-updated reference rates.
Number Base Converter
Convert numbers between binary, octal, decimal, hexadecimal and any base 2–36.
Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers.
Number to Words Converter
Spell out any number in English words, or format a dollar amount for a check.
Metric, imperial and US customary, side by side
Every converter here uses exact, internationally defined conversion factors (for example, one inch is exactly 2.54 centimeters and one pound is exactly 0.45359237 kilograms). Type a value once and each page also shows it in every other unit, which is handy for recipes, shipping, travel and homework.
For numbers rather than measurements, use the number base converter for binary and hex, the Roman numeral converter, or number to words for writing checks.
Frequently asked questions
Is a US gallon the same as a UK gallon?
No. A US liquid gallon is 3.785 liters, while an imperial (UK) gallon is 4.546 liters. The volume converter lists both.
How precise are the conversions?
Results are calculated with the exact defined factors and shown to up to eight significant decimal places.