Centimeters and inches, sorted out
A centimeter is a hundredth of a meter. An inch is one of those stubborn imperial units that refuses to die, and these days it’s actually defined off the metric system: exactly 2.54 cm. That’s not a rounded approximation. It’s the legal definition, agreed internationally back in 1959.
So the math runs the other way too. One centimeter equals 0.393701 inches. Type a number on the left, read the answer on the right. The conversion fires the instant you type, and the whole thing happens on your device. Nothing gets uploaded, nothing waits on a server.
Where this comes up
Height is the big one. You measured a doorframe at 198 cm and the furniture listing only gives inches? 198 divided by 2.54 lands at 78 inches, which is 6 foot 6. Now you know the wardrobe won’t fit.
Screen sizes live in inches too. A monitor sold as “27 inch” measures its diagonal at 68.58 cm. Phone and tablet specs sometimes flip between the two depending on which region’s store page you’re reading.
Paper trips people up constantly. A4 is a metric size (21 by 29.7 cm), but Letter paper is defined in inches (8.5 by 11). Drop those numbers in and you’ll see why a US printer chokes on a document laid out for A4: Letter is wider and shorter.
A few exact figures
- 1 cm = 0.393701 in
- 10 cm = 3.93701 in
- 30 cm = 11.811 in (just under a foot)
- 100 cm = 39.3701 in
- 2.54 cm = 1 in exactly
That 30 cm row is worth remembering. A foot is 30.48 cm, so a “30 cm ruler” is fractionally shorter than a foot ruler. Close, but not identical.
Using the converter
Punch a value into the input. The result updates live, no button to press. The dropdown lets you swap the source or target unit, so if you’d rather go inches to centimeters or jump to millimeters, you don’t need a different page. Below the field there’s a reference table covering the common values, handy when you just want to eyeball a conversion without typing.
Rounding is set to a sensible number of decimals for everyday use. If you need machinist-grade precision, remember the underlying ratio is exact, so you can always scale 2.54 yourself.
Common questions
How many inches is 1 cm?
0.393701 inches. Roughly four tenths of an inch. For a fast mental estimate, divide centimeters by 2.5 and you’ll be within a percent.
Is the 2.54 conversion exact or rounded?
Exact. Since 1959 the inch has been defined as 2.54 cm, so there’s no measurement error hiding in that number. The 0.393701 going the other way is that exact ratio inverted, rounded for display.
How do I convert my height from cm to inches?
Divide your height in centimeters by 2.54. So 180 cm divided by 2.54 is about 70.9 inches. To get feet and inches, split that: 70.9 inches is 5 feet 10.9 inches.
Why does my answer differ slightly from another converter?
Almost always rounding. Some tools cut off at two decimals, others keep six. The ratio itself never changes. If two results disagree past the fourth decimal, one of them rounded early.
Does anything get sent to a server?
Nope. The calculation runs in JavaScript right in your browser. You could disconnect from the internet after the page loads and it would still work.
What’s 12 cm in inches?
12 cm is 4.7244 inches. About four and three quarter inches, if you’re marking it on a tape measure.