To convert centimeters to inches, divide by 2.54. So 10 cm is 3.94 inches, 30 cm is 11.81 inches and 100 cm is 39.37 inches. To go from inches to centimeters, multiply by 2.54. Both directions are exact, because the inch is defined as exactly 2.54 cm.
Why is an inch exactly 2.54 cm? #
Before 1959, the American inch and the British inch differed by a few millionths. That year the US, UK and several Commonwealth countries agreed on an international yard of exactly 0.9144 m, which makes the inch (1/36 of a yard) exactly 25.4 mm. NIST SP 811 lists it as an exact conversion. So there’s no rounding hidden in 2.54. Any error in your answer comes from rounding the result, not the factor.
The mental shortcut #
Multiply cm by 4, then divide by 10. That’s the same as multiplying by 0.4, and it’s about 1.6% high. 50 cm becomes 20 inches (exact: 19.69). For inches to cm, multiply by 2.5: 12 inches becomes 30 cm (exact: 30.48). Both are fine for a quick estimate and not fine for cutting anything.
How do you convert height from cm to feet and inches? #
- Divide the height in cm by 2.54 to get total inches.
- Divide the inches by 12. The whole number is feet.
- Whatever is left over is inches.
For 175 cm: 175 ÷ 2.54 = 68.9 inches. 68.9 ÷ 12 = 5 with 8.9 left over, so 5 ft 8.9 in, which most people would call 5'9".
| cm | Total inches | Feet and inches |
|---|---|---|
| 150 | 59.1 | 4 ft 11.1 in |
| 155 | 61.0 | 5 ft 1.0 in |
| 160 | 63.0 | 5 ft 3.0 in |
| 165 | 65.0 | 5 ft 5.0 in |
| 170 | 66.9 | 5 ft 6.9 in |
| 175 | 68.9 | 5 ft 8.9 in |
| 180 | 70.9 | 5 ft 10.9 in |
| 183 | 72.0 | 6 ft 0.0 in |
| 185 | 72.8 | 6 ft 0.8 in |
| 190 | 74.8 | 6 ft 2.8 in |
| 195 | 76.8 | 6 ft 4.8 in |
| 200 | 78.7 | 6 ft 6.7 in |
And the other way:
| Height | cm |
|---|---|
| 4'10" | 147.3 |
| 5'0" | 152.4 |
| 5'2" | 157.5 |
| 5'4" | 162.6 |
| 5'6" | 167.6 |
| 5'8" | 172.7 |
| 5'10" | 177.8 |
| 5'11" | 180.3 |
| 6'0" | 182.9 |
| 6'2" | 188.0 |
| 6'4" | 193.0 |
| 6'6" | 198.1 |
To convert feet and inches to cm, turn everything into inches first: 5'11" is 5 × 12 + 11 = 71 inches, and 71 × 2.54 = 180.34 cm.
cm to inches chart #
| cm | inches | inches | cm | |
|---|---|---|---|---|
| 1 | 0.39 | 1/4 | 0.64 | |
| 2 | 0.79 | 1/2 | 1.27 | |
| 3 | 1.18 | 1 | 2.54 | |
| 5 | 1.97 | 2 | 5.08 | |
| 10 | 3.94 | 3 | 7.62 | |
| 15 | 5.91 | 4 | 10.16 | |
| 20 | 7.87 | 6 | 15.24 | |
| 25 | 9.84 | 8 | 20.32 | |
| 30 | 11.81 | 10 | 25.40 | |
| 50 | 19.69 | 12 | 30.48 | |
| 75 | 29.53 | 24 | 60.96 | |
| 100 | 39.37 | 36 | 91.44 |
A 30 cm ruler is just under a foot (11.81 inches), and a meter is 3.37 inches longer than a yard.
Fractions of an inch in millimeters #
US tape measures are marked in fractions, usually down to 1/16 inch. Here’s what those marks are in millimeters (multiply by 25.4):
| Fraction | Decimal inch | mm |
|---|---|---|
| 1/16 | 0.0625 | 1.59 |
| 1/8 | 0.125 | 3.18 |
| 1/4 | 0.25 | 6.35 |
| 3/8 | 0.375 | 9.53 |
| 1/2 | 0.5 | 12.70 |
| 5/8 | 0.625 | 15.88 |
| 3/4 | 0.75 | 19.05 |
| 7/8 | 0.875 | 22.23 |
For millimeters to inches, divide by 25.4. A 6 mm drill bit is 0.236 inch, a little under 1/4 inch.
Worked examples #
A European clothing size chart lists a 96 cm chest. 96 ÷ 2.54 = 37.8 inches.
A 55-inch TV. The size is the diagonal: 55 × 2.54 = 139.7 cm. A 65-inch TV is 165.1 cm.
A4 paper vs US Letter. A4 is 21.0 × 29.7 cm, which is 8.27 × 11.69 inches, slightly narrower and taller than US Letter. Letter is 8.5 × 11 inches, or 21.59 × 27.94 cm. That’s why documents shift when you print a Letter file on A4.
A picture frame for a 20 × 25 cm photo. That’s 7.87 × 9.84 inches, so an 8 × 10 inch frame fits with a little room.
Converting cm and inches on your phone #
Convert Units Calculator converts between micrometers, millimeters, centimeters, meters, kilometers, inches, feet, yards and miles in its Length category, using the exact 2.54 cm inch. Type 175 with centimeters selected and the inches and feet appear together, along with every other length unit. Version 1.0.5 also understands feet-and-inches shorthand when you convert from feet: type 5'11" and it converts 5.9167 feet, which is 180.34 cm.
For longer distances, see km to miles. The metric to imperial conversion chart puts length, weight and volume on one page, and how to convert units explains the method behind all of them.
Frequently asked questions #
How many inches are in 1 cm? #
1 cm is 0.3937 inch, a little over a third of an inch. It takes 2.54 cm to make one inch.
What is 5'7" in cm? #
5'7" is 67 inches, and 67 × 2.54 = 170.18 cm, usually rounded to 170 cm.
What is 170 cm in feet? #
170 cm is 66.9 inches, which is 5 ft 6.9 in. Rounded to the nearest inch, that’s 5'7".
Is an inch 2.5 cm? #
Not quite. An inch is exactly 2.54 cm. Using 2.5 gets you within 1.6%, which is fine for estimating but adds up over long measurements: 100 inches comes out 4 cm short.
How many cm is a foot? #
One foot is 12 inches, which is exactly 30.48 cm.