📐 Free Unit Converter
Convert length, weight, temperature, speed, area, volume and data storage — here in one converter, or on a dedicated page for each.
Unit conversion is a daily task in engineering, science, cooking, fitness and international work. This converter handles length (metres to feet), weight (kg to lbs), temperature (Celsius to Fahrenheit), speed (km/h to mph), area, volume and data storage. Enter any value and instantly see all related conversions with a complete reference table. Everything runs in your browser.
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A dedicated page for each conversion
The converter above handles every category at once. These pages go deeper on one each, with reference tables and the definitions the figures rest on.
Length Converter
Centimetres to inches, metres to feet, kilometres to miles — nine units with exact factors.
Weight Converter
Kilograms to pounds, grams to ounces, stones and all three kinds of ton.
Temperature Converter
Celsius, Fahrenheit and Kelvin, all three linked so any one of them can be edited.
Data Storage Converter
Bytes to terabytes, with the 1000 and 1024 systems kept separate rather than blurred.
CSS Unit Converter
Pixels to rem, em, vh and vw, against the root and parent font sizes you set.
Number Base Converter
Binary, octal, decimal and hexadecimal, converted in every direction at once.
Unix Timestamp Converter
Epoch seconds to a readable date and back, in local time and UTC.
Frequently Asked Questions
Free Unit Converter — Length, Weight, Temperature and More
Convert between metric and imperial units instantly. Enter any value and get the result in all related units at once, with a full reference table for common conversions. All conversions run in your browser — no server, no upload, no account needed.
Unit Conversion Reference Guide
The most frequently needed conversions: 1 kilometre = 0.621371 miles, 1 kilogram = 2.20462 pounds, 0°C = 32°F (formula: F = C × 9/5 + 32), 1 litre = 0.264172 US gallons, 1 inch = 2.54 centimetres, 1 acre = 4,046.86 square metres, 1 kilobyte = 1,000 bytes as the SI standard and every drive maker define it, or 1,024 as Windows still counts it — the data storage converter keeps the two apart.
For web development unit conversions (px to rem, em, vh, vw), use the dedicated CSS Unit Converter. For programming and electronics (binary, hexadecimal, octal), use the Number Base Converter. For timestamp and epoch conversion, use the Unix Timestamp Converter.
Unit conversion is standardised internationally through the SI system (Système International d'Unités). The SI defines seven base units: the metre for length, kilogram for mass, second for time, ampere for electric current, kelvin for temperature, mole for amount of substance and candela for luminous intensity. All other units are derived from these. The imperial system used in the United States and some other countries uses older definitions that predate SI standardisation, which is why conversions involve non-round factors like 2.54 cm per inch rather than clean powers of 10.