Quick Answer
To convert between units, multiply the original value by the conversion factor between the two units, for example, to convert kilometers to miles, multiply by 0.621371.
What Is Unit Converter?
A unit converter translates a measurement from one system or unit to another, for example, converting kilometers to miles, kilograms to pounds, or Celsius to Fahrenheit. This is essential whenever you're working across the metric system (used by most of the world) and the imperial/US customary system (used primarily in the United States), or simply converting between different units within the same system (like centimeters to meters).
Most unit conversions are simple multiplication by a fixed conversion factor, since most units (length, weight, volume) scale linearly. Temperature is a notable exception, converting between Celsius, Fahrenheit, and Kelvin requires both multiplication and addition/subtraction, because these scales have different zero points, not just different unit sizes.
Common conversion categories include length (km/miles, m/feet, cm/inches), weight/mass (kg/lb, g/oz), volume (liters/gallons, ml/fl oz), speed (km/h to mph), and temperature (°C/°F/K), each with its own specific conversion factor or formula.
How to Use
- 1Select the category of measurement you want to convert (length, weight, temperature, volume, or speed).
- 2Select the unit you're converting from and the unit you're converting to.
- 3Enter the value you want to convert.
- 4The calculator instantly shows the converted result.
Formula
Converted Value = Original Value × Conversion Factore.g. km to miles: × 0.621371
°F = (°C × 9/5) + 32°C = (°F − 32) × 5/9Example: Converting 100 kilometers to miles
- Value = 100 km
- Conversion factor (km to miles) = 0.621371
- Result = 100 × 0.621371
Tips & Things to Know
- Temperature conversions cannot be done by simple multiplication alone, always use the full formula with both multiplication and addition/subtraction for Celsius, Fahrenheit, and Kelvin.
- When precision matters (engineering, medical dosing, cooking at scale), use enough decimal places in your conversion factor, rounding too early can introduce meaningful errors in further calculations.
- Double-check whether a 'ton' refers to a metric ton (1,000 kg), a US short ton (2,000 lb), or a UK long ton (2,240 lb), these are different units that are easy to confuse.
- For everyday use (cooking, travel, fitness), rounded conversions are usually fine, but for scientific, legal, or financial contexts, use exact conversion factors.