cm to inches: How to Convert Centimeters to Inches

By the Tool Goodie Team · Updated July 4, 2026 · 4 min read

To convert centimeters to inches, divide the number of centimeters by 2.54. So 30 cm ÷ 2.54 = 11.81 inches. This works because one inch is defined as exactly 2.54 cm. To go the other way — inches to centimeters — multiply by 2.54 instead. Below you'll find a quick estimate, a reference table, and how to turn a height like 170 cm into feet and inches.

Key takeaways

cm → inches: divide by 2.54. inches → cm: multiply by 2.54.
1 inch = exactly 2.54 cm (an exact, defined value).
Quick estimate: divide cm by 2.5 (slightly high but close).
Convert any length with the length converter.

The formula

inches = centimeters ÷ 2.54
centimeters = inches × 2.54

Since 1959 the inch has been internationally defined as exactly 2.54 centimeters, so this conversion is precise, not a rounded approximation. Every accurate ruler, tape measure and converter uses the same 2.54 factor.

Quick mental estimate

For a rough figure without a calculator, divide by 2.5 instead of 2.54 — it's easier and only a whisker off:

25 cm ÷ 2.5 = 10 inches (exact: 9.84)
100 cm ÷ 2.5 = 40 inches (exact: 39.37)

Good enough for "will this fit on the shelf?" — use the exact formula for anything that has to be precise.

cm to inches table

Centimeters	Inches
1 cm	0.39 in
5 cm	1.97 in
10 cm	3.94 in
20 cm	7.87 in
30 cm	11.81 in
50 cm	19.69 in
100 cm	39.37 in

Convert instantly: the free Length Converter handles cm, inches, feet, meters, miles and more — type a value and read the answer, with the exact rate shown underneath.

Converting height: cm to feet and inches

Height is the most common reason people convert cm to inches, and it takes one extra step. First convert cm to total inches (÷ 2.54), then split into feet and inches (12 inches = 1 foot):

170 cm → 170 ÷ 2.54 = 66.9 inches → 66.9 ÷ 12 = 5 feet, with 6.9 inches left over → 5' 7"
180 cm → 180 ÷ 2.54 = 70.9 inches → 5' 11"
160 cm → 160 ÷ 2.54 = 63.0 inches → 5' 3"

Divide the total inches by 12 to get the feet, and whatever's left is the inches.

Frequently asked questions

How do you convert cm to inches?

Divide the number of centimeters by 2.54 to get inches, because one inch is defined as exactly 2.54 cm. For example, 30 cm ÷ 2.54 = 11.81 inches.

How many inches is 170 cm?

170 cm is about 66.9 inches, which is 5 feet 7 inches. To convert to feet and inches, divide the total inches by 12 for the feet and take the remainder as inches.

Is 1 inch exactly 2.54 cm?

Yes. Since 1959 the inch has been internationally defined as exactly 2.54 centimeters, so the conversion is exact rather than an approximation.