Unit Converter — Free Online Tool
Convert between metric and imperial units in one click — kilometers to miles, kilograms to pounds, Celsius to Fahrenheit, and dozens more across length, weight, and temperature.
What is the Unit Converter?
The world runs on two measurement systems, and they collide constantly: recipes in cups vs grams, road signs in miles vs kilometers, weather in Fahrenheit vs Celsius. Mental conversion is error-prone (remember the Mars Climate Orbiter, lost to a metric/imperial mix-up), so a reliable converter saves real mistakes.
This tool converts through base units — every length goes via meters, every weight via kilograms — so any pair converts consistently. Temperature is special: it needs an offset as well as a scale factor, because 0°C isn't “no temperature.” The converter handles those shifts for Celsius, Fahrenheit, and Kelvin automatically.
How to use this calculator
- Choose the measurement type (length, weight, or temperature).
- Enter the value to convert.
- Pick the from and to units.
- Click Convert — swap units anytime with the same tool.
Formula
Frequently asked questions
How many kilometers is a mile?
Exactly 1.609344 km. So 5 miles ≈ 8.05 km.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. 20°C = 68°F. Our converter does it instantly.
How many pounds in a kilogram?
2.20462 lb per kg. 70 kg ≈ 154.3 lb.
Why is temperature conversion different?
Temperature scales have different zero points, not just different sizes — so conversion needs adding/subtracting an offset, unlike length or weight.