Free Cm to Inches Converter

What is a centimetre?

A centimetre (cm) is one hundredth of a metre: 1 cm = 0.01 m. It is the everyday metric step for lengths too small for metres and too big for millimetres — body measurements, furniture dimensions, rainfall totals and heights on European documents are all usually given in centimetres.

The spelling is centimetre in British and European English and centimeter in American English; the symbol cm and the length are identical. Ten centimetres make a decimetre, one hundred make a metre, and one centimetre holds exactly ten millimetres.

What is an inch?

An inch (in) is an imperial and US customary unit of length, equal to exactly 25.4 millimetres since the International Yard and Pound Agreement of 1959. Twelve inches make one foot, and thirty-six make one yard.

Inches are still the everyday unit for screen sizes, bicycle wheels, pipe fittings and clothing in the United States and the United Kingdom, and for television and laptop screens even in metric countries. Because the inch is now defined in metric terms, converting between inches and centimetres is exact rather than approximate.

How to use this converter

1. Type your length in the centimetres box — the inch value updates as you type, with no button to press.
2. Read the result line: the exact decimal inches, the reverse rate, and the nearest 1/16-inch fraction for reading a tape measure.
3. To go the other way, type in the inches box instead, or press Swap direction to flip the converter and carry the converted value over as the new input.
4. Decimals are welcome: 12.5 cm converts just as easily as 12 cm.

Centimetres to inches formula

Let L_cm be the length in centimetres and L_in be the same length in inches. The two directions are:

• Inches from centimetres: L_in = L_cm ÷ 2.54
• Centimetres from inches: L_cm = L_in × 2.54

The number 2.54 is exact: since 1959 the inch has been defined as 25.4 mm, so 1 in = 2.54 cm with no rounding at all. Any rounding you see comes only from how many decimal places are displayed. For the wider story of both systems, see our metric vs imperial conversion guide for Europe.

Worked example

Centimetres to inches conversion table

Inches are shown to four decimal places; the fraction column rounds to the nearest 1/16 inch, the smallest mark on most tape measures.

Everyday benchmarks: centimetres you already know in inches

These are the centimetre lengths people meet most often, with their inch equivalents:

• A4 paper, long side — 29.7 cm = 11.69 in. Just under a foot tall, which is why A4 looks short next to US Letter paper.
• Standard 30 cm ruler — 30 cm = 11.81 in. A school ruler is close to, but not quite, a 12-inch ruler.
• Cabin bag limit — 55 cm = 21.65 in. The common 55 × 40 × 20 cm airline limit is about 21.7 × 15.7 × 7.9 in.
• Average adult height — 170 cm = 66.93 in. That is 5 ft 7 in in the feet-and-inches style used in the UK and US.
• Smartphone height — 15 cm = 5.91 in. A typical large phone is just under 6 inches tall.
• Interior doorway — 200 cm = 78.74 in. A standard European door is about 6 ft 7 in tall.

For lengths beyond centimetres and inches, the Free Unit Converter covers more units in one place, including metres, feet, miles, weight and temperature.

Frequently asked questions

How do you convert cm to inches?

Divide the centimetre value by 2.54. For example, 50 cm ÷ 2.54 = 19.685 in. The factor 2.54 is exact, because the inch has been defined as 25.4 mm since 1959, so the only rounding is in how many decimal places you display.

What is 100 cm in inches?

100 cm is 39.3701 inches. On a tape measure that is 39 3/8 inches to the nearest 1/16 inch. One hundred centimetres is exactly one metre, so this is also the length of a metre in inches.

Is 1 inch exactly 2.54 cm?

Yes. Since the International Yard and Pound Agreement of 1959, the inch has been defined as exactly 25.4 millimetres, which is exactly 2.54 cm. It is a definition, not a measurement, so it never changes and never needs rounding.

How many inches is 30 cm?

30 cm is 11.811 inches, just under 12 inches. That is why a 30 cm school ruler is slightly shorter than a 12-inch ruler: it is missing about 0.19 inches, or 3/16 of an inch.

How do I read centimetres on an inch tape measure?

Convert first, then use the fraction column: the converter shows the nearest 1/16 inch, which is the smallest mark on most tape measures. For example, 10 cm is 3.937 in, which reads as 3 15/16 in on the tape — one sixteenth under 4 inches.

What is 170 cm in inches and feet?

170 cm is 66.9291 inches. Dividing by 12 gives 5 feet with 6.93 inches left over, so 170 cm is 5 ft 7 in rounded to the nearest inch — a very common adult height.

Why does my tape measure show fractions instead of decimals?

Inch tape measures are marked in fractions — halves, quarters, eighths and sixteenths — because the imperial system grew up around dividing lengths in half. The decimal value from this converter is exact; the fraction is the nearest mark you can actually read on the tape.

Can I convert inches back to cm here?

Yes. Type in the inches box and the centimetre value updates instantly, or press Swap direction to flip the converter. For the dedicated reverse tool, use the Free Inches to Cm Converter.

Sources

• NIST Special Publication 811 — Guide for the Use of the International System of Units (SI), conversion factors for the inch, foot and yard.
• BIPM SI Brochure — the International System of Units, definitions of the metre, centimetre and millimetre.
• International Yard and Pound Agreement, 1959 — 1 yard = 0.9144 m exactly, giving 1 in = 25.4 mm and 1 ft = 0.3048 m exactly.

Disclaimer: conversions use the exact defined factor (1 in = 2.54 cm); check critical cuts against a physical tape measure before you cut.

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