CM to Inches

How to convert centimeters to inches

There are exactly 2.54 centimeters in one inch, so to go from centimeters to inches you divide by 2.54.

Example: a 30 cm ruler is 30 ÷ 2.54 = 11.81 inches. A 70 cm waist is 70 ÷ 2.54 ≈ 27.6 inches.

Centimeters to inches table

Height in cm to feet and inches

Height is the most common reason people convert centimeters, and it needs a second step: divide by 2.54 for total inches, then divide by 12 to get feet with the remainder as inches.

Worked example: 170 cm ÷ 2.54 = 66.93 in. 66.93 ÷ 12 = 5 feet with 6.93 inches left over, so 170 cm is about 5 ft 7 in.

Doing it in your head

• Rough answer: divide by 2.5 — this gives a figure about 1.6% too high, which is close enough for a quick sense of scale.
• Better: divide by 2.5, then take off about one part in sixty. For 100 cm that is 40 − 0.6 = 39.4 in, against the true 39.37 in.
• Anchors worth memorising: 2.5 cm ≈ 1 in, 30 cm ≈ 1 ft, 100 cm ≈ 39.4 in.
• Reverse direction: multiply inches by 2.5 and add 2% for centimeters.

Where the number 2.54 comes from

The relationship is exact, not approximate. Under the 1959 international yard and pound agreement, the countries still using imperial units defined one inch as precisely 2.54 centimeters, tying the inch to the metric system by definition.

That is why conversions never lose accuracy in either direction: any rounding you see comes from the decimals you choose to display, not from the conversion itself.

Screens, paper and everyday objects

How many decimals you actually need

One decimal place of an inch is about 2.5 millimeters, and two decimal places is about a quarter of a millimeter. That tells you how far to round: a height, a screen or a piece of furniture needs one decimal at most, while anything machined or printed to size deserves two — or is better kept in millimeters entirely.

Rounding early is the usual source of error. If a calculation has several steps, carry the full figure through and round once at the end, otherwise small rounding errors accumulate into a visible gap.

Clothing, sewing and furniture

Garment measurements are the other everyday case, and they are where a wrong conversion is most expensive. A pattern quoting a 70 cm waist means 27.6 inches, not 27 — and a sewing pattern that is half an inch out will not fit.

Furniture listings are worth converting before you buy rather than after it arrives: a sofa advertised at 200 cm wide is 78.7 inches, which is nearly six and a half feet and decides whether it fits a wall or gets returned.

When you need fractions instead of decimals

Tape measures in inches are marked in halves, quarters, eighths and sixteenths, not decimals, so 11.81 in is not directly readable. Multiply the decimal part by 16 to get sixteenths: 0.81 × 16 ≈ 13, so 30 cm is about 11 and 13/16 inches.

For DIY work, rounding to the nearest sixteenth is within 1.6 mm — fine for wood, but not for anything that has to fit precisely, where it is safer to keep working in millimeters.