A centimeters to inches calculator converts a metric length to the US/UK customary inch using the exact factor 1 cm = 0.3937 in (equivalently, divide cm by 2.54). Enter a value in centimeters and the calculator returns the inch equivalent.
Useful for shopping in the US with metric labels, reading international clothing sizes, converting screen and TV diagonals, height conversions for travel and immigration paperwork, and any setting where the same length needs both systems.
Key takeaway
The cm-to-inch ratio is exact, the inch is defined as exactly 2.54 cm, so dividing centimeters by 2.54 returns the precise inch value with no rounding. For mental math, "divide by 2.5" gets you within 1.6% of the exact answer, which is plenty close for everyday use like clothing sizes, heights, and casual measurements.
How it's calculated
The conversion:
inches = centimeters ÷ 2.54
Equivalently, inches = centimeters × 0.3937007874.... The 2.54 figure is the international inch defined exactly as 25.4 mm; its reciprocal is the cm-to-inch factor, 0.39370... (an infinite repeating decimal, the irrationality is just because we're inverting a 5/2-style ratio).
Because the inch is bigger than the centimeter, the inch number is always smaller than the centimeter number for any positive length, a useful sanity check.
Source: Inverse of NIST inch, 1 cm = 0.3937007874 in (exact)
Examples
30 cm, about 1 foot
- Length 30 cm
30 cm converts to 11.81 in, just under 1 foot (12 in). Useful anchor: a 30 cm ruler is approximately a foot long but ~2 mm shorter. Mental shortcut: 30 ÷ 2.5 = 12 (within 1.6% of actual 11.81).
180 cm, typical adult height
- Length 180 cm
180 cm converts to 70.87 in, about 5'11" (5 ft 10⅞ in). Just below the 6-foot mark, which lands at 182.88 cm. The metric world often uses 180 cm as a rough "tall" threshold the way the US uses 6 feet.
Frequently asked questions
How do I convert centimeters to inches?
Divide by 2.54 for the exact answer (or multiply by 0.3937, which is the same thing). For mental math, "divide by 2.5" is within 1.6% of the right value across all sizes, fine for clothing, height, and small DIY measurements. So 75 cm ÷ 2.54 = 29.53 in (or 75 ÷ 2.5 = 30, close).
Is 1 inch exactly 2.54 cm?
Yes, by international agreement since 1959. The inch was defined as exactly 25.4 mm (= 2.54 cm) when the US and Commonwealth countries unified their length definitions. There's no rounding at any decimal place; the number is exact by definition. (A historical "US survey inch" had a slightly different value but has been deprecated since 2022.)
How do I convert someone's metric height to feet and inches?
Two-step. First, divide cm by 2.54 to get total inches. Then divide by 12 to get whole feet, with the remainder as inches. So 175 cm: 175 ÷ 2.54 ≈ 68.9 in. 68.9 ÷ 12 = 5 with remainder 8.9 → 5'8.9" (or about 5'9"). For quick mental conversion, anchor at 100 cm = 3'3" and adjust from there.
Why do screen sizes use inches even in metric countries?
Because the screen industry is dominated by manufacturers using US-customary units in their product naming, even for products sold worldwide. A "55-inch TV" stays "55 inches" in Europe and Asia, because translating to "139.7 cm" loses the marketing-friendly round number. The diagonal is what's quoted; aspect ratio (e.g., 16:9) determines the actual width and height in either unit system.