Unit Converter
Convert between units across twelve measurement families at once, seeing the value in every related unit rather than one at a time, with exact and defined factors shown.
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Every unit in the family at once, not one conversion at a time
Most converters make you pick a source and a target and give you a single number. That is the wrong shape for the way conversion questions actually arrive: you rarely know in advance which unit you want, and comparing three candidates means running the tool three times. This one takes a value and shows it in every unit of its family simultaneously, so a measurement in feet appears in metres, inches, yards and miles together and you pick the one that reads best.
Most conversion factors are exact definitions, not measurements
The inch has been exactly 25.4 millimetres since the international yard and pound agreement of 1959, the pound is exactly 0.45359237 kilograms, and the calorie is exactly 4.184 joules. These are definitions, so conversions between them are exact up to floating point. A few are not: the nautical mile is exact at 1852 metres, but a mile per hour compared to a knot inherits both definitions and the result is exact as well. This tool marks which relationships are defined and which are conventional, because a rounded value used in a spreadsheet propagates.
Temperature is the exception that catches people out
Every other family converts by multiplication alone, so doubling the input doubles every output. Temperature does not, because Celsius and Fahrenheit have different zero points as well as different degree sizes. Twenty degrees Celsius is not twice ten degrees Celsius in any meaningful sense, and converting a temperature difference uses a different rule from converting a temperature. The tool shows both, since mixing them up is the single most common temperature conversion error.
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Frequently Asked Questions
Is the inch to millimetre conversion exact?
Yes. Since the 1959 international yard and pound agreement the inch is defined as exactly 25.4 millimetres, so every imperial to metric length conversion is exact by definition rather than measured.
Why is temperature handled differently from other units?
Because Celsius and Fahrenheit have different zero points as well as different degree sizes, so the conversion is affine rather than a simple multiplication. That also means converting a temperature difference uses a different rule from converting a temperature.
What is the difference between a US and an imperial gallon?
The US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres, about 20% larger. Both are shown separately because recipes and fuel figures from different countries are not interchangeable.
Are KB and KiB the same thing?
No. A kibibyte is exactly 1024 bytes while a kilobyte is 1000 bytes under the SI convention. Both are listed so you can see the gap, which reaches roughly 10% by the time you get to terabytes.
Why does my converted value show so many digits?
Because the tool shows the full precision the conversion produces rather than rounding for you. Rounding is a presentation decision that depends on your use, and a value rounded early then used in further arithmetic accumulates error.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Pick a family, enter a value and choose its unit.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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