cm to inches formula
To convert centimeters to inches, multiply the number of centimeters by 0.393700787402. In symbols: in = cm × 0.393700787402.
One centimeter equals 0.393700787402 inches, and one inch equals 2.54 centimeters. The inch is defined as exactly 2.54 centimeters, so 1 cm is 1/2.54 = 0.393700787 in.
Worked example
Suppose you have 170 centimeters and need the answer in inches.
- Write the formula: in = cm × 0.393700787402.
- Put in the number: 170 × 0.393700787402 = 66.92913386.
- Round to suit the job. 66.93 in is accurate enough for most everyday uses.
So 170 cm is 66.92913386 in. To check, convert back: 66.92913386 in is 170 cm.
Common centimeters to inches values
| centimeters (cm) | inches (in) |
|---|---|
| 1 | 0.3937007874 |
| 2 | 0.7874015748 |
| 5 | 1.968503937 |
| 10 | 3.937007874 |
| 20 | 7.874015748 |
| 50 | 19.68503937 |
| 100 | 39.37007874 |
Reference points
Some familiar amounts in centimeters, converted to inches:
- 15 cm, a standard school ruler: 5.90551 in
- 30 cm, a typical ruler or 12 in laptop width: 11.811 in
- 100 cm, one meter: 39.3701 in
- 170 cm, an average adult height: 66.9291 in
Where you will use it
Clothing sizes, TV and phone screens, picture frames and height charts mix centimeters and inches. Online shops from the US and Europe often list sizes in only one of them.
Quick mental math
Multiply by 0.4 and take off 2 percent; 170 cm gives 68 minus 1.4, close to the true 66.9 in. Rule of thumb: multiply by 0.4. For 170 cm this gives 68 in against the exact 66.93, an error of 1.6 percent.
Going the other way
Need the reverse? Use the inches to cm converter. For comparison, 1 in is 2.54 cm. To compare every length unit at once, open the length converter.
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