Convert units online
0.621371
Miles
Switch between length (meters, kilometers, miles, feet, inches...), weight (kilograms, pounds, ounces...), and temperature (Celsius, Fahrenheit, Kelvin) conversions, all in one tool. Pick a category, choose your units, and enter a value to see the converted result instantly. Everything runs in your browser; nothing you enter is sent anywhere.
Exact conversion factors
The imperial-to-metric factors used here are the internationally agreed exact definitions rather than rounded approximations: one inch is exactly 25.4 millimetres, one pound is exactly 0.45359237 kilograms, and one mile is exactly 1609.344 metres. Those are definitional rather than measured values, so conversions are precise to the digits shown rather than accumulating rounding error.
Temperature is a different kind of conversion
Length and weight conversions are simple multiplications because the scales share a zero point — zero metres is zero feet. Temperature scales do not: zero Celsius is 32 Fahrenheit, so conversion requires both a multiplication and an offset. This is why you cannot convert a temperature difference the same way as a temperature, and why doubling 10°C does not give you the Fahrenheit equivalent of 20°C.
Kelvin has no negatives
Kelvin starts at absolute zero, the coldest physically possible temperature, which is why Kelvin values are never negative. Entering a Celsius value below −273.15 will produce a negative Kelvin figure that has no physical meaning — the arithmetic works but the result describes nothing real. It is a useful sanity check when converting scientific data.
Frequently asked questions
- What unit categories are supported?
- Length, weight, and temperature. Each category has its own set of common units to convert between.
- How accurate are the conversions?
- Conversions use standard, precise conversion factors (e.g. 1 mile = 1609.344 meters exactly), so results are accurate to the precision shown.
- Is my data sent anywhere?
- No, conversion happens locally in your browser using JavaScript. Nothing is transmitted.
- How precise are these conversions?
- They use exact internationally-defined factors, so results are accurate to the digits displayed rather than approximations.
- Why can I not convert a temperature difference?
- Temperature scales have different zero points, so converting a difference needs the ratio only, without the offset. Converting each endpoint and subtracting gives the right answer.