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Centimeters to Inches (cm to in)

Convert centimeters to inchs instantly. The formula is inches = cm ÷ 2.54 — one inch is exactly 2.54 centimeters by international agreement, so dividing by 2.54 is the exact conversion. Everything is computed locally in your browser; nothing is uploaded.

Centimeter (cm)Inch (in)

1 cm = 0.3937 in · 1 cm = 0.3937 in

Quick reference — cm to in

How to convert cm to in

The exact conversion factor between centimeters and inchs gives the formula inches = cm ÷ 2.54. One inch is exactly 2.54 centimeters by international agreement, so dividing by 2.54 is the exact conversion.

For a rough mental estimate, remember that 1 cm = 0.3937 in. To go the other way, see the inches to centimeters converter — it uses the reciprocal factor.

Worked examples

Example: convert 5 cm to in. Apply the formula — inches = cm ÷ 2.54 — and you get 1.97 in. Reverse-check it by using the inches to centimeters to come back to 5 cm; if you do not land on the original number, a factor was inverted.

Example: convert 100 cm to in. Apply the formula — inches = cm ÷ 2.54 — and you get 39.37 in. Reverse-check it by using the inches to centimeters to come back to 100 cm; if you do not land on the original number, a factor was inverted.

Where the factor comes from

The modern factors date to the international yard and pound agreement of 1959, in which the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa agreed that one yard equals exactly 0.9144 meters. That single definition pins down every length factor on this page: the inch is exactly 2.54 cm, the foot exactly 0.3048 m, and the mile exactly 1,609.344 m. Before 1959, national standards differed by parts per million — irrelevant for a recipe, but critical for surveying and engineering, which is why the agreement exists.

Common mistakes

Reusing the factor backwards. 1 inch = 2.54 cm does not mean 1 cm = 2.54 in. The reverse factor is 0.3937. If a result looks too large by roughly 6.5×, you inverted the factor.

Rounding mid-calculation. Converting meters → feet → inches in two steps rounds twice. Convert directly to the smallest unit you need, then round once at the end.

Mixing up US survey units. The US survey mile (used in old land records) differs from the international mile by about 2 ppm. For anything except geodetic work, the international factor on this page is correct.

Quick mental shortcuts

Mental shortcuts: cm → in ≈ divide by 2.5 (then subtract 4%); in → cm ≈ ×2.5 (then add 4%); km → mi ≈ ×0.6 (a marathon, 42.195 km, is 26.2 mi); m → ft ≈ ×3.3 (a 2 m door is about 6.6 ft).

Common cm to in conversions

Centimeter (cm)	Inch (in)
1	0.3937
5	1.97
10	3.94
20	7.87
50	19.69
100	39.37

FAQ

How do I convert cm to in?

inches = cm ÷ 2.54. One inch is exactly 2.54 centimeters by international agreement, so dividing by 2.54 is the exact conversion.

What is 5 cm in in?

5 cm equals 1.97 in. Use the converter above for any value.

How do I convert in back to cm?

Use the reverse conversion — see our inches to centimeters converter. The calculator above also shows the reciprocal rate.

Is the cm-to-in conversion exact?

Yes — modern units are defined by international agreement with exact factors (e.g. 1 inch = 2.54 cm exactly). Results are rounded only for display.

More conversions

in → cm mm → in in → mm m → ft ft → m km → mi mi → km kg → lb lb → kg g → oz oz → g °C → °F °F → °C gal → L L → gal g → cup cup → g g → tbsp tbsp → g g → ml ml → g ml → cup cup → ml fl oz → ml ml → fl oz

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