CM to Inches Converter

Enter a length in centimeters to get inches as an exact decimal, with the formula worked using your own number and a reference chart from 1 to 100 cm.

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How to convert cm to inches

A centimeter is one hundredth of a meter; an inch is a US and imperial unit of length. The two are linked by one exact factor, so converting between them is a single division (or multiplication in reverse), the same for a screw, a shelf, or a person's height.

The formula

inches = centimeters ÷ 2.54   or   centimeters = inches × 2.54

2.54 is exact, not measured, because 1 inch is defined as exactly 25.4 mm, which is exactly 2.54 cm.

Worked example

30 cm to inches:

30 ÷ 2.54 = 11.811 in (6 significant figures). That is 11 whole inches plus about 0.81 in left over, or roughly 11 13/16 in on a tape measure.

Reverse direction: 11.8 in to centimeters: 11.8 × 2.54 = 29.972 cm.

Reference chart: cm to inches

cmInches (decimal)
1 cm0.393701 in
2 cm0.787402 in
3 cm1.1811 in
4 cm1.5748 in
5 cm1.9685 in
6 cm2.3622 in
7 cm2.75591 in
8 cm3.14961 in
9 cm3.54331 in
10 cm3.93701 in
15 cm5.90551 in
20 cm7.87402 in
25 cm9.84252 in
30 cm11.811 in
35 cm13.7795 in
40 cm15.748 in
45 cm17.7165 in
50 cm19.685 in
55 cm21.6535 in
60 cm23.622 in
65 cm25.5906 in
70 cm27.5591 in
75 cm29.5276 in
80 cm31.4961 in
85 cm33.4646 in
90 cm35.4331 in
95 cm37.4016 in
100 cm39.3701 in

The exact factor: why 2.54 cm is exactly 1 inch

Before July 1, 1959, the US inch and the UK (imperial) inch were not quite identical: each country had its own legal definition, and the two differed by roughly two parts per million, a gap of a few millionths of an inch. The International Yard and Pound Agreement, signed by the United States, the United Kingdom, Australia, Canada, New Zealand, and South Africa, fixed the international yard at exactly 0.9144 meters, which fixes the inch at exactly 25.4 mm, or exactly 2.54 cm, with zero remaining uncertainty.

Height in cm to inches

Converting a height works the same way as any other length: divide centimeters by 2.54. A common shorthand is that 5 cm is close to (but not exactly) 2 inches, which is why quick mental conversions of height can drift by half an inch or more over a full body height. For a version built specifically around height, with feet-and-inches formatting, see the Height Converter.

When precision matters: woodworking vs machining

A carpenter marking a board off a metric plan can round to the nearest 16th of an inch without consequence: the difference is a fraction of a millimeter, invisible in a stud wall or a shelf. A machinist working to a 0.01 mm tolerance cannot round that way; a 16th-inch step is worth about 1.6 mm, easily enough to bind a fitted part. If your source measurement is metric and your target hardware is metric, it is often simplest to skip the conversion altogether and work in centimeters or millimeters throughout.

Related conversions

Working in millimeters instead? Try the MM to Inches Converter. Going the other direction from inches to centimeters as your primary input? See the Inches to CM Converter. Need feet instead? Use the Inches to Feet Converter, or for meters and feet see the Meters to Feet Converter.

Frequently asked questions

How many inches is 1 cm?

1 cm equals 0.393701 in, to 6 significant figures. Since 1 inch is exactly 2.54 cm, 1 cm is exactly 1/2.54 in, which is a repeating decimal in inches, so 0.393701 is a rounded (not exact) value.

How do I convert cm to inches?

Divide the centimeter value by 2.54, since 1 inch is defined as exactly 2.54 cm. For example, 30 cm / 2.54 = 11.811 in. The 2.54 factor itself carries no uncertainty; only the final decimal you keep is rounded.

What is 100 cm in inches?

100 cm equals 39.3701 in, to 6 significant figures. That is just under 3 feet 3.4 inches. 100 cm is 1 meter, so this is also the meters-to-inches conversion for exactly 1 meter.

Why is 1 inch exactly 2.54 cm?

Since the 1959 International Yard and Pound Agreement, the inch has been defined as exactly 25.4 mm, which is exactly 2.54 cm. Before that date, slightly different US and UK inch definitions meant the conversion carried a tiny, real ambiguity of a few millionths of an inch.

How accurate is a cm to inches conversion for height?

The math is exact to as many digits as you want; the accuracy limit is your original measurement, not the conversion. A height measured to the nearest half centimeter cannot become more precise just by converting it, so round your inches result to match the precision of the original centimeter reading. See our Height Converter for a version built specifically for people.

Is a cm to inches conversion the same for any length?

Yes. The factor 2.54 applies to every length, whether it is a small part, a person's height, or a room dimension. There is no separate formula for height or for furniture; centimeters convert to inches the same way every time.

What is 5 cm in inches?

5 cm equals 1.9685 in, to 6 significant figures. That is close to, but not exactly, 2 inches, a common source of confusion when eyeballing metric-to-imperial conversions.

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