Example 1
- Direction: cm to inches
- 180 cm
70.8661 in
180 / 2.54 = 70.8661 in.
CM to Inches Calculator
Enter a length in centimeters or inches — pick the direction from the list. Formula: inches = cm ÷ 2.54, centimeters = inches × 2.54. At 180 cm the result is 70.8661 in; at 30 cm it is 11.811 in; at 1 cm it is 0.3937 in. The calculator uses the international inch (exactly 2.54 cm) and does not split the result into feet and inches.
Result
Enter a length in centimeters or in inches. The result shows up here.
The default direction is centimeters to inches. When you start from inches, open Inches to cm. Threads and sheet: millimeters and inches. Height in feet: cm to feet and inches.
How the result is calculated
Length180 cm
Constant2.54
Result70.8661 in
The model on this page is the international inch from 1959: exactly 25.4 mm, or 2.54 cm per inch. Centimeters to inches means dividing by that constant. Inches to centimeters means multiplying by the same constant. The result shows four decimal places. At 180 cm: 180 / 2.54 = 70.8661 in. At 1 cm the result is 0.3937 in. At 30 cm it is 11.811 in.
The other way, 1 in × 2.54 = 2.54 cm. The 2.5 cm-per-inch shortcut is close, but it is not exact. The reciprocal of the constant is about 0.3937007874 in per centimeter; the result for 1 cm rounds to 0.3937. A 30 cm school ruler is 11.811 in, not a clean 12 — twelve inches are 30.48 cm.
The default direction is centimeters to inches, which matches this page’s intent. The sibling inches-to-centimeters page starts from inches. Here you can also pick inches to cm from the list without changing the formula. A comma and a period mean the same fraction. Zero is allowed. A negative number is rejected.
The calculator does not assemble 5 ft 11. Millimeters belong on a separate page for threads and sheet metal. This is not a height converter in meters — when someone gives 1.80 m instead of 180 cm, open meters and feet.
How to use
- Leave the direction on Cm to inches, or pick Inches to cm.
- Enter a length, for example 180.
- Click Calculate. 180 cm gives 70.8661 in. 1 cm gives 0.3937 in.
- The other way, enter 1. The result is 2.54 cm.
- Feet-and-inches and millimeters live on separate pages. This page keeps the cm and in pair.
Formula
Model: the international inch (1959 definition) — exactly 2.54 cm per inch (25.4 mm).
in = cm / 2.54
cm = in × 2.54
The result rounds to four decimal places. The reciprocal of the constant is about 0.3937007874 in/cm; at 1 cm the calculator shows 0.3937 in.
2.54 cm and the cm–in pair
The international inch is exactly 2.54 cm. 180 cm is 70.8661 in. 1 cm is 0.3937 in, not a “0.4” shortcut.
- cm
- Centimeter. 180 cm = 70.8661 in. 30 cm = 11.811 in. Default input on this page.
- in
- International inch. 1 in = 2.54 cm. This is not a 5 ft 11 split.
- 2.54
- 1959 constant. Division yields inches; multiplication yields centimeters.
- 0.3937
- 1 cm on this page to four places. Not a 0.4 shortcut.
Examples
Three sets from the same formula. The first two start from centimeters; the third starts from inches.
Example 2
- Direction: cm to inches
- 30 cm
11.811 in
30 / 2.54 = 11.811 in. Twelve inches are 30.48 cm.
Example 3
- Direction: inches to cm
- 1 in
2.54 cm
1 × 2.54 = 2.54 cm. The same constant the other way.
Related calculators
Frequently asked questions
What does this calculator convert?
Length between centimeters and inches. Formula: in = cm / 2.54 and cm = in × 2.54, shown to four decimal places. At 180 cm the result is 70.8661 in.
Where does the 2.54 cm constant come from?
It is the international inch from 1959: exactly 25.4 mm, or 2.54 cm per inch. That also yields about 0.3937007874 in per centimeter; in the result 1 cm is 0.3937 in.
Does the result print feet and inches?
No. You get one number in inches or cm. A 5 ft 11 split belongs on the cm to feet and inches page.
How do the cm-to-inches and inches-to-cm directions work?
The Direction list sets whether the length field is in centimeters or in inches. By default the page converts cm to inches. The other option uses the same constant the other way: 1 in is 2.54 cm.
Can length be negative?
No. Zero is allowed and still converts to zero. A negative number is rejected.
Is the 2.5 cm-per-inch shortcut exact?
No. An inch is exactly 2.54 cm. A 2.5 cm shortcut is too loose for height and for frames.
Is a tailor inch different?
Not on this page. The calculator uses 2.54 cm from 1959.
Do commas work in the length field?
Yes. A comma and a period mean the same fractional value. 15.6 in works the same as 15,6.
How is this different from millimeters and inches?
Same family, different scale. Threads and sheet metal usually use mm. Height and waist usually use cm. Do not mix 180 cm with 1800 mm in the same field.
Where do I convert inches to centimeters first?
On the inches to centimeters page you start from inches. Here the default direction is centimeters to inches, though both pages use the same 2.54 constant.
How many inches are 10 cm and 100 cm?
Ten centimeters are about 3.9370 in. One hundred centimeters are about 39.3701 in. Divide cm by 2.54.
How many cm are 1 inch and 12 inches?
One inch is exactly 2.54 cm. Twelve inches are 30.48 cm — the same as one foot.
How many inches is 175 cm of height?
One hundred seventy-five centimeters is about 68.8976 in. A feet-and-inches split belongs on the cm to feet and inches page.
How many cm is a 55-inch TV?
Fifty-five inches is 139.7 cm of diagonal (55 × 2.54). The calculator returns one number in cm or inches, not a separate panel size.
How is this page different from mm to inches?
Here the input unit is centimeters. Threads and sheet metal usually use millimeters — that pair is on the mm to inches page.
Does the result replace a tailor’s tape?
No. The calculator only converts units. For sewing and fit, take the reading from your own tape.
Knowledge sources
The international inch is exactly 2.54 cm (1959 definition, 25.4 mm). NIST SP 330 and BIPM provide SI context.
Page updated November 3, 2026.