A unit converter lets you instantly convert between measurement units — length, weight, temperature, area, speed, volume, and more — without formulas or manual math. Our free online unit converter covers all common unit systems including metric, imperial, and US customary units.
Unit Conversion Categories
| Category | Common Units |
|---|---|
| Length | mm, cm, m, km, inches, feet, yards, miles |
| Weight / Mass | mg, g, kg, tonnes, ounces, pounds, stones |
| Temperature | Celsius, Fahrenheit, Kelvin |
| Area | cm², m², km², in², ft², acres, hectares |
| Volume | ml, L, fl oz, cups, pints, quarts, gallons |
| Speed | m/s, km/h, mph, knots |
| Data Size | bits, bytes, KB, MB, GB, TB |
| Time | seconds, minutes, hours, days, weeks, years |
Most Common Unit Conversions
| Conversion | Formula | Quick Example |
|---|---|---|
| Celsius to Fahrenheit | (°C × 9/5) + 32 | 100°C = 212°F |
| Fahrenheit to Celsius | (°F − 32) × 5/9 | 72°F = 22.2°C |
| Kilometres to Miles | km × 0.621371 | 10 km = 6.21 miles |
| Miles to Kilometres | miles × 1.60934 | 10 miles = 16.09 km |
| Kilograms to Pounds | kg × 2.20462 | 70 kg = 154.3 lbs |
| Pounds to Kilograms | lbs × 0.453592 | 150 lbs = 68.0 kg |
| Inches to Centimetres | in × 2.54 | 12 in = 30.48 cm |
| Litres to Gallons (US) | L × 0.264172 | 10 L = 2.64 gal |
How to Convert Units Online
- Open the free unit converter at ReadyGoTools
- Select the unit category (length, weight, temperature, etc.)
- Enter the value you want to convert
- Choose the source unit and the target unit
- The converted value appears instantly
Metric vs Imperial Units
Most of the world uses the metric system (SI units), while the United States primarily uses the US customary system (similar to imperial). The UK uses a mix of both. When traveling, cooking with international recipes, or working on global projects, a unit converter is essential. See our free online calculators for more math tools.
Temperature Conversion Quick Reference
| Celsius | Fahrenheit | Context |
|---|---|---|
| 0°C | 32°F | Water freezes |
| 20°C | 68°F | Room temperature |
| 37°C | 98.6°F | Human body temperature |
| 100°C | 212°F | Water boils |
| -40°C | -40°F | Celsius and Fahrenheit are equal |
FAQ — Unit Converter
How many centimetres are in an inch?
There are exactly 2.54 centimetres in one inch. This is a defined conversion — 1 inch = 2.54 cm exactly.
How do you convert Celsius to Fahrenheit?
Multiply the Celsius temperature by 9/5 (or 1.8), then add 32. Example: 25°C × 1.8 = 45, plus 32 = 77°F.
How many pounds are in a kilogram?
One kilogram equals 2.20462 pounds. Conversely, one pound equals 0.453592 kilograms.
Is there a free unit converter with no sign-up?
Yes. ReadyGoTools provides a completely free unit converter — covering length, weight, temperature, volume, speed, and more — with no account required and instant results.
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