How to use the cm to inches converter
Type a length in centimeters and the answer in inches appears as you type. The big number is rounded to two decimal places, which is what most people need. Under it you get the exact value to four places, the nearest mark on a tape measure (to the 1/16 inch), the same length in feet and inches, and the length in millimeters and meters. Press the arrows to go the other way, from inches to centimeters. You can type a unit if your number is in millimeters or meters, such as 12 mm or 1.7 m, and on the inches side you can type fractions or feet, like 66 1/2 or 5 ft 7 in. The picture slides a metric rule and an inch tape to your length so you can see where the two scales meet. The Height tab is for people, and the Chart tab prints a table. Nothing you type leaves your device unless you make a share link.
The formula
centimeters = inches × 2.54
The number 2.54 is not rounded. Since 1959, the inch has been defined as exactly 2.54 centimeters, by the international yard and pound agreement among the national standards laboratories of the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa, in effect from July 1, 1959. That makes the conversion exact in one direction: any number of inches times 2.54 gives a centimeter value that ends. Going the other way, dividing by 2.54 usually gives a decimal that goes on forever, because 2.54 is 127/50 and 127 is a prime number. So 1 cm is 0.393700787… inches, and every page that shows "0.3937" has rounded it. This calculator keeps the exact ratio and rounds only at the end.
A worked example
A shelf is 30 cm deep. Divide by 2.54: 30 ÷ 2.54 = 11.811 inches, or about 11.81 inches. On a tape measure that is between 11 3/4 and 11 7/8 inches; the nearest 1/16 mark is 11 13/16 inches, which is only about 0.0015 of an inch away. In feet and inches it is 0 ft 11.81 in. Going back, 11.81 × 2.54 = 29.9974 cm, not 30, which shows why you should convert from the number you measured and not from a rounded answer.
Reading the answer on a tape measure
A US tape measure is marked in inches split into halves, quarters, eighths and sixteenths, not in decimals. To mark 11.81 inches you need a fraction. Multiply the decimal part by 16 and round: 0.81 × 16 = 12.96, which rounds to 13, so the mark is 13/16. The calculator does this for you and says how far the mark is from the exact length. If the decimal part rounds to 16/16, the length goes up to the next whole inch. This page rounds to the nearest 1/16 inch, the finest mark along most of a typical builder's tape (some also mark 1/32 near the end). When a cut has to be closer than that, measure in millimeters with a metric rule instead.
Centimeters to feet and inches
For longer lengths and for height, inches alone are hard to picture. Divide the inches by 12: the whole number is feet and what is left over is inches. 170 cm is 66.93 inches; 66 ÷ 12 is 5 with 6 left over, so 170 cm is 5 ft 6.93 in, which most people round to 5 ft 7 in. A meter is 39.37 inches, a little more than a yard (36 inches). The Height tab does this with a picture of a person against a wall marked both ways.
Common conversions
| Centimeters | Inches | On a tape |
|---|---|---|
| 1 cm | 0.39 in | 3/8 in |
| 2.54 cm | 1 in | 1 in |
| 5 cm | 1.97 in | 1 15/16 in |
| 10 cm | 3.94 in | 3 15/16 in |
| 15 cm | 5.91 in | 5 7/8 in |
| 30 cm | 11.81 in | 11 13/16 in |
| 100 cm | 39.37 in | 39 3/8 in |
Where the numbers come from
The definition of the inch as 0.0254 meter exactly is listed by the National Institute of Standards and Technology (NIST) in its guide to SI units, Special Publication 811, which this site's unit converter was checked against. Before 1959 the US inch came from the meter: the 1893 Mendenhall Order made the meter the country's standard of length, using the 1866 law's ratio of 39.37 inches to a meter, so the old US inch was about 2.540005 cm. That older value lived on only in the US survey foot used for land surveying, and NIST and NOAA retired the survey foot after December 31, 2022. For everyday lengths the difference is far too small to see. There is no building code for this conversion; the factor is a legal definition.
What people use it for
- Clothing, shoe and bag sizes listed in centimeters.
- Furniture and appliance sizes from a European or Asian maker.
- Screen and picture frame sizes, and paper sizes such as A4 (21 × 29.7 cm).
- Height on a passport, a medical form or a sports roster.
- Woodworking plans in metric when your tape is in inches.
Common mistakes
- Multiplying when you should divide. Centimeters are smaller, so the inch number is always smaller. If your answer got bigger, you multiplied.
- Using 2.5. It is close enough for a guess, but on 200 cm it is off by almost 1.3 inches.
- Converting a rounded answer back. Keep the number you measured and convert from it.
- Mixing millimeters and centimeters. 12 mm is 1.2 cm, not 12 cm. Type the unit and the calculator reads it.
- Reading a decimal as a fraction. 5.5 inches is 5 1/2 inches, but 5.10 inches is not 5 10/16. It is 5 and 1.6 sixteenths, so the nearest mark is 5 1/8.
Questions
How many inches is 1 cm?
1 cm is 0.393700787 inches, about 0.39 inch, a hair over 3/8 inch on a tape measure.
Is 2.54 exact or rounded?
Exact. The inch is defined as 2.54 centimeters, so inches to centimeters is always exact. Centimeters to inches is usually a repeating decimal, so it has to be rounded at some point. This page rounds only at the end.
How do I convert cm to feet and inches?
Divide the centimeters by 2.54 to get inches, then divide the inches by 12. The whole number is feet and the rest is inches. 180 cm is 70.87 inches, which is 5 ft 10.87 in.
Can I use metric?
Yes. The Imperial | Metric switch sets how you type a height (centimeters, or feet and inches) and which table comes first in the chart. The page opens in the system your browser's region uses and remembers your choice on this device.
Can I share an answer?
Yes. Share makes a link with a picture of both rulers for Facebook, a link you can copy, and a short video for TikTok made on your device. The link keeps only the length you typed and which way you converted, for 90 days.