Rulers in the UK, Canada and Europe are marked in centimeters, while tape measures, furniture listings and height charts in the US still use inches and feet. If you buy a TV in one country and a wall bracket in another, or fill in a US form with a height you only know in centimeters, you need to switch between the two quickly and correctly. This guide shows the exact method, a shortcut you can do in your head, and how to handle heights.
The exact relationship
Since the 1959 international yard and pound agreement, the inch has been defined as exactly 2.54 centimeters. Nothing is rounded, so you can convert in either direction with no loss of accuracy.
| Unit | Equals |
|---|---|
| 1 inch (in) | 2.54 cm, exactly |
| 1 centimeter (cm) | 0.393701 in (rounded) |
| 1 foot (ft) | 12 in = 30.48 cm, exactly |
| 1 meter (m) | 39.3701 in = 3.28084 ft |
Formula: centimeters to inches
Divide the number of centimeters by 2.54:
inches = centimeters ÷ 2.54
Worked example: 30 cm ÷ 2.54 = 11.81 in. A 30 cm school ruler is just under a foot long.
Going the other way, multiply:
centimeters = inches × 2.54
Worked example: a 55-inch TV has a 55 × 2.54 = 139.7 cm diagonal.
A mental shortcut that is accurate to about 1.6%
Dividing by 2.54 is awkward without a calculator. Instead:
- Multiply the centimeters by 4.
- Divide by 10 (move the decimal point one place left).
That multiplies by 0.4 instead of 0.3937, so the answer is about 1.6% too high. For 50 cm: 50 × 4 = 200, then 20.0 in. The exact answer is 19.69 in, so the shortcut is off by only a third of an inch.
Tip: for inches to cm, multiply by 2.5 and add a little. 20 in × 2.5 = 50, plus a bit gives 50.8 cm (exact).
Converting a height in cm to feet and inches
Heights are the most common reason people search for this conversion. Use three steps:
- Convert to inches: cm ÷ 2.54.
- Divide the inches by 12. The whole number is the feet.
- Multiply the leftover fraction by 12 to get the inches.
Worked example: 175 cm ÷ 2.54 = 68.90 in. 68.90 ÷ 12 = 5.74, so 5 feet. 0.74 × 12 = 8.9, so the height is 5 ft 9 in (5 ft 8.9 in before rounding).
Note: most forms round to the nearest whole inch. Round only at the very last step, otherwise small errors add up.
Quick chart
| Centimeters | Inches | Feet and inches |
|---|---|---|
| 1 cm | 0.39 in | |
| 5 cm | 1.97 in | |
| 10 cm | 3.94 in | |
| 25 cm | 9.84 in | |
| 50 cm | 19.69 in | 1 ft 7.7 in |
| 100 cm | 39.37 in | 3 ft 3.4 in |
| 150 cm | 59.06 in | 4 ft 11.1 in |
| 160 cm | 62.99 in | 5 ft 3.0 in |
| 170 cm | 66.93 in | 5 ft 6.9 in |
| 180 cm | 70.87 in | 5 ft 10.9 in |
| 190 cm | 74.80 in | 6 ft 2.8 in |
| 200 cm | 78.74 in | 6 ft 6.7 in |
Common mistakes
- Multiplying instead of dividing. If your answer in inches is bigger than the centimeters, you multiplied by 2.54 by mistake. Inches are always the smaller number.
- Writing 5.74 ft as 5 ft 74 in. The decimal part of feet is a fraction of 12, not of 100. Convert it as shown above.
- Mixing millimeters and centimeters. Engineering drawings are usually in mm. Divide mm by 25.4 to get inches.
Try it with the converter
For any value, use our length converter, which shows the formula and a worked example for every pair of units. For height specifically, the height converter gives feet and inches directly.
Frequently asked questions
Is 1 inch exactly 2.54 cm? Yes. It has been fixed at exactly 2.54 cm since 1959 in the US, UK, Canada and other Commonwealth countries.
How many cm is 6 feet? 6 ft = 72 in, and 72 × 2.54 = 182.88 cm.
Why do the UK and Canada use both systems? Both countries adopted metric units officially, but heights, road distances (in the UK) and many trades still use imperial units out of habit, so people meet both every day.
More from the blog
Have expertise to share? Write for pakmath.com.