How to Convert Centimeters to Inches

Centimeters and inches both measure length, one metric and one imperial. Converting between them rests on a single exact number. Here it is, with a worked example, the trick for heights, the reverse direction, and a shortcut for quick estimates.

The short version: divide the centimeters by 2.54 to get inches. That one figure covers everything, from a screen size to a person’s height.

The centimeters to inches factor

One inch equals exactly 2.54 centimeters. This is a defined value, not a rounded one, so it never drifts no matter how large the measurement.

inches = centimeters / 2.54

Because the relationship is exact, you can trust it for precise work like cutting material or sizing a frame. There is no approximation hiding in the 2.54.

A worked example, step by step

Say a shelf is 30 cm deep and you want that in inches.

1. Take the length: 30 cm.
2. Divide: 30 / 2.54 = 11.81.

So 30 cm is about 11.8 inches, just under a foot. The same step works at any size. A 50 cm width is 50 / 2.54 = 19.69, or roughly 19.7 inches. Only the starting number changes.

Turning a height into feet and inches

Heights are the most common reason to convert, and they need one more step. First get total inches, then split into feet and inches, since twelve inches make a foot.

1. A height of 170 cm: 170 / 2.54 = 66.93 inches.
2. Divide by 12: 66.93 / 12 = 5 feet, with 6.93 left over.
3. So 170 cm is about 5 feet 7 inches.

The leftover inches come from the remainder after the feet. Round to the nearest inch for everyday use, which is why 6.93 reads as 7.

Going the other way

To convert inches back to centimeters, multiply by 2.54 instead of dividing.

centimeters = inches × 2.54

Say a box is 12 inches wide. Multiply: 12 × 2.54 = 30.48. So 12 inches is 30.48 cm, which is a foot in metric terms. The factor is the same; you just multiply to go this direction.

A quick mental shortcut

When you only need a rough figure, multiply the centimeters by 0.4. Dividing by 2.54 is close to dividing by 2.5, and multiplying by 0.4 is the same move. For 25 cm, 25 × 0.4 = 10 inches. The exact answer is 9.84, so the estimate is within a fifth of an inch.

The shortcut runs slightly high because 0.4 is a touch more than 1 over 2.54. It is fine for picturing a size in your head, but use the full 2.54 for anything you cut or build.

Handy reference points

• 1 inch is exactly 2.54 cm.
• 10 cm is about 3.94 inches.
• 30 cm is about 11.8 inches, close to a foot.
• 100 cm is about 39.4 inches.

These anchors let you scale quickly. Since 10 cm is near 4 inches, 20 cm is near 8 inches, and 50 cm is near 20 inches. The factor holds, so doubling the centimeters doubles the inches.

Screen and TV sizes

Screens are a frequent reason to convert, since televisions and monitors are sized by the diagonal in inches almost everywhere. If a listing gives the diagonal in centimeters, divide by 2.54 to get the familiar inch figure.

A screen sold as 140 cm is 140 / 2.54, which is about 55 inches, a common television size. The measurement runs corner to corner, not across the width, so always convert the diagonal rather than the side to compare two sets.

Common mistakes to avoid

• Multiplying when you should divide. Centimeters to inches divides by 2.54; inches to centimeters multiplies by it.
• Forgetting to split a height into feet. Total inches divided by 12 gives the feet, and the remainder is the inches.
• Treating the 0.4 shortcut as exact. It runs a little high, so use 2.54 for precise work.
• Mixing up millimeters and centimeters. Ten millimeters make one centimeter, so check the unit on your ruler first.

Frequently asked questions

What is the exact factor? One inch is exactly 2.54 centimeters. Divide centimeters by 2.54 for inches, and multiply inches by 2.54 to go back.

How do I convert a height like 170 cm? Divide by 2.54 for total inches, then divide that by 12. The whole number is the feet and the remainder is the inches, so 170 cm is about 5 feet 7 inches.

Is the times 0.4 trick accurate? It is a quick estimate that runs slightly high. Fine for a rough sense of a size, but use 2.54 when you cut or build.

How many centimeters are in a foot? A foot is 12 inches, which is 12 × 2.54, or 30.48 centimeters.

Do I need to do this by hand? No. The factor is handy to know, but a converter is faster and handles feet and meters too. Use the one below to switch units in a second.