ToolBox FreeCONVERTER
Unit Converter
Convert between everyday units of length, weight, temperature, area and volume.
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How to use the Unit Converter
Choose a category, enter a value and pick the units to convert from and to. The result updates as you type, and the table underneath shows the same amount in every unit of that category. Use Swap units to reverse the direction.
Conversions go through a base unit (metre, kilogram, square metre, litre or kelvin) using exact definitions, such as 1 inch = 25.4 mm and 1 pound = 0.45359237 kg.
Examples and uses
- 5 km ≈ 3.1069 miles
- 100 °F ≈ 37.78 °C
- 1 US gallon ≈ 3.7854 litres
Limitations and good to know
Gallons, pints, cups and fluid ounces are US customary units except where marked UK, and they differ from their UK equivalents. Results show up to 10 significant digits, and very large or small values appear in scientific notation. Temperatures below absolute zero are rejected.
Frequently asked questions
Are the conversion factors exact?
They use internationally defined values, for example 1 inch = 25.4 mm and 1 lb = 0.45359237 kg.
Why are US and UK gallons different?
They are separate historical units: a US gallon is about 3.785 litres and a UK (imperial) gallon is about 4.546 litres.
How is temperature converted?
Through kelvin, using the standard formulas, so Celsius, Fahrenheit and Kelvin all convert correctly rather than by a simple multiplier.
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