Unit Converter
Local only — nothing is uploaded unless you save or share it.
kg to lbs, mm to inches, cm to feet — every everyday unit, in your browser.
- Pick what you are converting — length, weight, temperature and so on
- Choose the units to convert from and to
- Type a number; the answer appears as you type
Common conversions
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About this tool
Most unit conversions are one number and one multiplication, and the reason they are worth a tool is that the multiplication has to be the right one. An inch is defined as exactly 25.4 millimetres and a pound as exactly 0.45359237 kilograms — these are definitions rather than measurements, and this converter uses them in full rather than the rounded versions that make every answer look plausible and put you a little way out. Temperature is the awkward one, because Fahrenheit has an offset as well as a scale, so −40°C and −40°F really are the same temperature and a converter that treats it as a simple ratio gets it wrong. Data sizes are the other trap: a kilobyte is 1,000 bytes and a kibibyte is 1,024, they differ by 2.4% at that size and by 10% at terabytes, and both are in daily use — so both are listed rather than one being quietly chosen for you. Length, weight, temperature, volume, area, speed, data and time are all here, converting as you type. Everything runs locally, so nothing you enter is transmitted, logged, or stored.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54. The inch has been defined as 25.4 millimetres since 1959, so it is an exact figure rather than a measured one — which is why this converter uses it in full instead of rounding. Going the other way, one centimetre is about 0.3937 inches.
How do I convert mm to inches?
Choose length and type the millimetres. An inch is exactly 25.4 mm — that is a definition rather than a measurement — so mm to inches is one division and this does it to as many decimals as you need, which matters when the number is a drill bit or a screen bezel rather than a rough size.
How do I convert kg to lbs?
Pick weight, type the kilograms, and the pounds appear as you type — one kilogram is 2.20462 pounds, and the conversion here uses the full figure rather than the 2.2 people do in their heads, which drifts by half a pound on a suitcase. It works in both directions, so lbs to kg is the same box.
How do I convert kg to pounds?
Multiply by 2.20462. A pound is defined as exactly 0.45359237 kilograms, so 70 kg is about 154.3 lb and 11 stone is about 69.9 kg. Pick Weight above and the conversion happens as you type.
Why is −40 the same in Celsius and Fahrenheit?
Because Fahrenheit has both a different scale and a different zero point, and the two scales cross at −40. That crossing is also a good check of any temperature converter: if it does not return −40, it is treating the conversion as a simple ratio and every other answer will be wrong too.
Is a kilobyte 1,000 bytes or 1,024?
Both conventions exist, which is why both are listed. A kilobyte is 1,000 bytes and a kibibyte is 1,024; storage manufacturers use the first and most operating systems report the second. They differ by 2.4% at kilobytes and about 10% at terabytes, which is why a 1 TB drive shows as roughly 931 GB.
Are my conversions sent to a server?
No. Everything is calculated in your browser, so nothing is transmitted and nothing is stored. You can disconnect from the internet after the page loads and it keeps working.
Which gallon does it use?
Both. US and UK gallons are listed separately because they are genuinely different — a UK gallon is about 4.55 litres and a US gallon about 3.79, a difference of a fifth. Picking one silently is how a recipe or a fuel figure ends up badly out.
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