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Formula
inches = centimeters ÷ 2.54
- centimeters
- the length you measured in cm
- 2.54
- the exact number of centimeters in one inch, fixed by international agreement in 1959
- inches
- the same length in inches; divide by 12 for feet
The cm to inches formula
There is only one number to remember: an inch is exactly 2.54 centimeters. To go from cm to inches, divide by 2.54. To go the other way, multiply.
Take a 24 cm pan: 24 ÷ 2.54 = 9.449 inches, so it is a “9½-inch” pan in a US recipe. This calculator does the division for you and adds the two forms people actually need in daily life: the length in feet and inches for heights and furniture, and the length rounded to the nearest 1/16 inch so you can find it on an imperial tape measure.
Mental math shortcuts
Dividing by 2.54 in your head is awkward. These shortcuts get you close:
- Multiply by 4, then divide by 10. 1 cm ≈ 0.4 in, so 35 cm ≈ 14 in. The true answer is 13.78 in; this shortcut always reads about 1.6% high.
- Every 5 cm is about 2 inches. 20 cm ≈ 8 in (exact: 7.87), 50 cm ≈ 20 in (exact: 19.69).
- 30 cm is about a foot. A foot is 30.48 cm, so a 30 cm school ruler is about half a centimeter short of 12 inches.
- Going back: inches × 2.5. 8 in ≈ 20 cm (exact: 20.32).
The converter shows the exact figure and a quick-check line, so you can see how far the estimate is off.
Cm to inches conversion chart (1 to 100 cm)
The decimal column is rounded to two places; the tape-measure column is the nearest 1/16 inch. All values were calculated with the converter.
| Centimeters | Inches | Tape measure |
|---|---|---|
| 1 cm | 0.39 in | 3/8 in |
| 2 cm | 0.79 in | 13/16 in |
| 3 cm | 1.18 in | 1 3/16 in |
| 4 cm | 1.57 in | 1 9/16 in |
| 5 cm | 1.97 in | 1 15/16 in |
| 6 cm | 2.36 in | 2 3/8 in |
| 7 cm | 2.76 in | 2 3/4 in |
| 8 cm | 3.15 in | 3 1/8 in |
| 9 cm | 3.54 in | 3 9/16 in |
| 10 cm | 3.94 in | 3 15/16 in |
| 12 cm | 4.72 in | 4 3/4 in |
| 15 cm | 5.91 in | 5 7/8 in |
| 20 cm | 7.87 in | 7 7/8 in |
| 25 cm | 9.84 in | 9 13/16 in |
| 30 cm | 11.81 in | 11 13/16 in |
| 40 cm | 15.75 in | 15 3/4 in |
| 50 cm | 19.69 in | 19 11/16 in |
| 60 cm | 23.62 in | 23 5/8 in |
| 70 cm | 27.56 in | 27 9/16 in |
| 75 cm | 29.53 in | 29 1/2 in |
| 80 cm | 31.5 in | 31 1/2 in |
| 90 cm | 35.43 in | 35 7/16 in |
| 100 cm | 39.37 in | 39 3/8 in |
Cm to inches for height: feet and inches
Height is the most common reason to convert cm to inches. US forms, dating apps and sports rosters ask for feet and inches, while passports and doctors in most countries record centimeters.
| Height | Feet and inches | Total inches |
|---|---|---|
| 150 cm | 4 ft 11.1 in | 59.1 in |
| 155 cm | 5 ft 1 in | 61 in |
| 160 cm | 5 ft 3 in | 63 in |
| 165 cm | 5 ft 5 in | 65 in |
| 170 cm | 5 ft 6.9 in | 66.9 in |
| 175 cm | 5 ft 8.9 in | 68.9 in |
| 180 cm | 5 ft 10.9 in | 70.9 in |
| 185 cm | 6 ft 0.8 in | 72.8 in |
| 190 cm | 6 ft 2.8 in | 74.8 in |
If you are converting a height to work out body mass index, the BMI calculator accepts centimeters or feet and inches directly.
Cm to inches for waist size, screens and paper
- Waist and inseam. US jeans are sized in inches. A 76 cm waist is size 30, 86 cm is 34 and 96.5 cm is 38. Measure where the waistband sits, not your natural waist, for the best match.
- Screens. TVs, monitors and phones are sold by the diagonal in inches. A 65-inch TV is 165.1 cm corner to corner.
- Bike frames and luggage. Frame sizes are often quoted in cm on road bikes and inches on mountain bikes. Airline carry-on limits such as 56 × 36 × 23 cm work out to roughly 22 × 14 × 9 in.
- Paper and photos. A4 paper is 21 × 29.7 cm, or about 8.27 × 11.69 in, slightly narrower and taller than US Letter (8.5 × 11 in).
Common mistakes
- Multiplying instead of dividing. Multiplying 10 cm by 2.54 gives 25.4, which is inches to cm. Inches are bigger, so the inch number must be smaller.
- Reading decimal inches as a fraction. 5.5 in is 5 1/2 in, but 5.3 in is not 5 3/8 in; 0.3 in is closer to 5/16. Use the tape-measure line.
- Mixing decimal feet with inches. 5.7 ft is 5 ft 8.4 in, not 5 ft 7 in.
- Rounding a height too early. Rounding 2.54 to 2.5 makes a 180 cm person 6 ft 0 in instead of 5 ft 10.9 in.
For conversions between other units, including meters, miles and nautical miles, use the full length converter.
Worked examples
Height in inches
A person is 172 cm tall. The result also shows feet and inches.
Inputs: Value = 172; From = Centimeters (cm); To = Inches (in)
inches = centimeters ÷ 2.54 → 172 ÷ 2.54 = 67.716535 in quick check: 172 × 0.4 ≈ 68.8 in
Answer: 172 cm = 67.716535 in (5 ft 7.72 in, about 67 11/16 in)
Laptop screen in centimeters
Laptop screens are sold by their diagonal in inches. Convert 15.6 in to cm.
Inputs: Value = 15.6; From = Inches (in); To = Centimeters (cm)
centimeters = inches × 2.54 → 15.6 × 2.54 = 39.624 cm
Answer: 15.6 in = 39.624 cm (1 ft 3.6 in, about 15 5/8 in)
Waist measurement for jeans
A tape measure reads 81 cm around the waist. Which US jeans size is closest?
Inputs: Value = 81; From = Centimeters (cm); To = Inches (in)
inches = centimeters ÷ 2.54 → 81 ÷ 2.54 = 31.889764 in quick check: 81 × 0.4 ≈ 32.4 in
Answer: 81 cm = 31.889764 in (2 ft 7.89 in, about 31 7/8 in)
A few millimeters on a ruler (edge case)
A 4 mm gap, rounded to the nearest 1/16-inch mark on an imperial ruler.
Inputs: Value = 0.4; From = Centimeters (cm); To = Inches (in)
inches = centimeters ÷ 2.54 → 0.4 ÷ 2.54 = 0.15748 in quick check: 0.4 × 0.4 ≈ 0.16 in
Answer: 0.4 cm = 0.15748 in (0.16 in, about 3/16 in)
Assumptions and limitations
- 1 inch is exactly 2.54 cm, so 1 cm = 0.393700787… in. The decimal result is rounded to 6 places, feet-and-inches to 0.01 in.
- The tape-measure line rounds to the nearest 1/16 inch (about 1.6 mm), the finest mark on most US tape measures, and reduces the fraction (8/16 shows as 1/2).
- You can also convert inches back to centimeters, or use millimeters, meters or feet; the feet-and-inches and fraction lines always describe the same length in inches.
- Lengths can't be negative.
Frequently asked questions
How do you convert cm to inches?
Divide the centimeters by 2.54. For example, 45 cm ÷ 2.54 = 17.72 in. Multiplying by 0.3937 gives the same answer to four decimals.
How many inches is 1 cm?
One centimeter is 0.3937 inches, a little under 4/10 of an inch. On a tape measure it falls just above the 3/8-inch mark.
How do I convert cm to feet and inches for height?
Divide by 2.54 to get inches, then divide by 12. The whole number is feet and the remainder is inches. 168 cm ÷ 2.54 = 66.14 in, which is 5 ft 6.14 in, or about 5 ft 6 in.
Is 2.54 an exact number or a rounded one?
It is exact. Since the international yard and pound agreement of 1959, the inch has been defined as exactly 25.4 millimeters, so cm to inches conversions don't depend on any measured value.
How do I convert inches back to cm?
Multiply by 2.54. A 32-inch TV is 32 × 2.54 = 81.28 cm on the diagonal. Switch the From and To units in the converter to do this.
How do I read the fraction result on a tape measure?
The converter rounds to the nearest 1/16 inch. 13 cm is 5.118 in, which rounds to 5 2/16, shown as 5 1/8 in. Count to the 5-inch mark, then two of the smallest ticks past it.
Sources
- SI Units – Length — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- Unit Conversion — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- Approximate Conversions from Metric to U.S. Customary Measures — National Institute of Standards and Technology (NIST). Checked October 12, 2026.