Converters tools
Length, weight and temperature with exact factors shown.
Nothing is uploaded. This tool runs entirely inside your browser tab. Your files and figures stay on your device - we never receive them, so we cannot read, store or lose them.
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cm to inches
Convert centimetres to inches and back using the exact international factor, with a reference chart and the formula shown.
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kg to lbs
Convert kilograms to pounds and back with the exact international factor, plus a reference chart and stone conversions.
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Celsius to Fahrenheit
Convert °C to °F and back with the formula shown, plus a reference chart of everyday and body temperatures.
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Feet to metres
Convert feet to metres and back with the exact international factor, plus a chart covering heights, room sizes and altitudes.
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Miles to km
Convert miles to kilometres and back with the exact factor, plus speed limits, running distances and a reference chart.
Exact factors, not rounded ones
Every metric-to-imperial factor on this site is the internationally agreed exact value from the 1959 International Yard and Pound Agreement - an inch is exactly 2.54 cm, a pound is exactly 0.45359237 kg, a mile is exactly 1,609.344 m. These are definitions, not measurements, and each converter shows the factor it used so you can check the arithmetic yourself.
Temperature works differently
Length and weight conversions are proportional: double the input, double the output. Temperature scales are affine - they have different zero points, so converting requires an offset as well as a ratio. That is why °C to °F needs the +32, and why you cannot convert a temperature difference the same way you convert a temperature.
Every page works in both directions
Each converter has two input boxes and swaps freely - type in either one and the other follows. The unit selectors cover the whole dimension, so the centimetres-to-inches page will just as happily convert nautical miles to millimetres if that is what you need.
Reference tables
Each page carries a printed conversion chart alongside the calculator, because a good many people arriving at a converter want to scan a table rather than type a number. The tables are generated from the same exact factors, so they never drift from the calculator above them.