Centimetres to inches
Convert centimetres to inches — type any value and get the answer instantly.
The conversion
One centimetre is 0.3937007874 inches, and one inch is exactly 2.54 centimetres. The inch has been defined as exactly 2.54 cm since 1959, so this is a definition rather than a measurement — the digits do not run out, they simply stop.
Dividing by 2.5 gets you close enough for most purposes: 30 cm ≈ 12 inches, and the true answer is 11.81.
Heights, and the trap in them
Converting a height like 175 cm gives 68.9 inches, which is not "5 foot 8.9". Feet are twelve inches, so it is 5 ft 8.9 in — divide by 12 and keep the remainder. Treating the decimal as inches is the single most common mistake here, and it is why the box above accepts 175 cm to ft directly.
Screens, paper and tyres
Screen sizes are quoted in inches diagonally: a 15.6-inch laptop is 39.6 cm corner to corner. Paper goes the other way — A4 is 21 × 29.7 cm, or 8.27 × 11.7 inches, which is why it never quite matches US Letter at 8.5 × 11.
Fractions
Imperial measurements are usually written in fractions rather than decimals: 0.5 in rather than 0.5000, and 3/8 rather than 0.375. For woodwork and plumbing, rounding to the nearest sixteenth is normal practice.
Clothing, shoes and the units that are not units
One warning. Shoe and clothing sizes look like measurements and are not — a US 9, a UK 8 and an EU 42 do not convert by any formula, because the scales are conventions that differ by manufacturer as much as by country. Any site offering a shoe-size "conversion" is showing you an average dressed up as arithmetic. Measure the foot in centimetres and use the maker's own chart.
Other units
The box takes anything — try 70 kg to lbs, 5 ft in cm or 180 c to f.
Common questions
How do I type a conversion?
Plainly: 70 kg to lbs, 5 ft in cm, 180 c to f. Abbreviations and full names both work.
Is a kilobyte 1000 or 1024 bytes?
1,024 here, matching operating systems. Drive makers use 1,000, which is why a 1 TB disk shows as 931 GB.
Why is temperature different?
The scales do not share a zero, so it is a multiplication and an offset rather than a simple factor.
Can it convert kg to metres?
No — those measure different things, so it explains rather than returning a meaningless number.
Is it accurate?
Conversions use exact defined factors where they exist: an inch is exactly 2.54 cm, a pound exactly 0.45359237 kg.