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To convert inches to centimeters, multiply the inch value by 2.54:
centimeters = inches × 2.54
The factor is exact: 1 inch = 2.54 centimeters. For example, 12 inches is 12 × 2.54 = 30.48 centimeters.
Inches-to-centimeters conversion formula
Use this formula for any whole number, decimal, or fraction:
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cm = in × 2.54
Written as a unit conversion, the calculation is:
inches × (2.54 cm ÷ 1 in) = centimeters
The in units cancel, leaving the answer in centimeters. The inch-to-centimeter factor is exact, not a rounded estimate. NIST defines one inch as exactly 2.54 centimeters, or 25.4 millimeters.
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Examples
| Inches | Calculation | Centimeters |
|---|---|---|
| 1 in | 1 × 2.54 |
2.54 cm |
| 5 in | 5 × 2.54 |
12.7 cm |
| 12 in | 12 × 2.54 |
30.48 cm |
| 36 in | 36 × 2.54 |
91.44 cm |
How to convert inches to centimeters
- Write down the measurement in inches.
- Multiply it by
2.54. - Label the result in centimeters.
- Round the result only if the measurement or the intended use requires it.
For example, to convert 7.5 inches:
7.5 × 2.54 = 19.05 cm
Therefore, 7.5 inches equals 19.05 centimeters.
Converting fractions of an inch
Convert the fraction to a decimal first, then multiply by 2.54. For example:
¼ inch = 0.25 inch
0.25 × 2.54 = 0.635 cm
So, ¼ inch equals 0.635 centimeters. The same method works for measurements such as ⅜, ½, or 1¾ inches.
| Fraction | Decimal inches | Centimeters |
|---|---|---|
| ¼ in | 0.25 | 0.635 cm |
| ½ in | 0.5 | 1.27 cm |
| ¾ in | 0.75 | 1.905 cm |
| 1¾ in | 1.75 | 4.445 cm |
Converting feet and inches
Do not multiply a notation such as 5 ft 6 in directly by 2.54. Convert the feet to inches first:
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- Multiply the feet by 12, because
1 ft = 12 in. - Add the remaining inches.
- Multiply the total by 2.54.
For 5 ft 6 in:
(5 × 12) + 6 = 66 in
66 × 2.54 = 167.64 cm
Thus, 5 feet 6 inches equals 167.64 centimeters.
Reverse conversion: centimeters to inches
To convert centimeters to inches, divide by 2.54:
inches = centimeters ÷ 2.54
For example:
30.48 ÷ 2.54 = 12 in
You can also multiply by the repeating decimal 0.3937007874…, but dividing by 2.54 is usually clearer. The commonly repeated instruction to “divide inches by 2.54” is backwards: division converts centimeters to inches, while inches-to-centimeters conversion requires multiplication.
Using Google Sheets
Google Sheets has a built-in CONVERT function. Its syntax is:
=CONVERT(value,"in","cm")
To convert 12 inches, enter:
=CONVERT(12,"in","cm")
The result is 30.48.
If cell A1 contains the inch measurement, use:
=CONVERT(A1,"in","cm")
Both "in" and "cm" are distance units, so Sheets can convert between them. The function returns an error when the starting and ending units belong to incompatible categories, such as converting feet to Celsius.
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Length, area, and volume are different conversions
The factor 2.54 applies to a linear measurement only. Do not use it unchanged for square inches or cubic inches.
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For area, square the linear conversion factor:
1 in² = (2.54 cm)² = 6.4516 cm²
Therefore, 10 in² equals 64.516 cm², not 25.4 cm².
Cubic inches
For volume, cube the factor:
1 in³ = (2.54 cm)³ = 16.387064 cm³
Therefore, 5 in³ equals 81.93532 cm³.
In Google Sheets, area and volume use separate unit codes, such as "in^2" and "in^3". Use the unit that matches the measurement rather than "in" for every type of result.
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How much should you round?
The conversion factor is exact, but the displayed answer does not always need every decimal place. Your rounding should reflect the precision of the original measurement and the purpose of the result.
| Use case | Possible reporting |
|---|---|
| Exact calculation or technical drawing | Keep the required decimal places, such as 30.48 cm |
| General size description | Round to a practical value, such as 30.5 cm |
| Rough mental estimate | Use approximately 2.5 cm per inch |
For a quick estimate, multiply inches by 2.5. For example, 12 inches is roughly 30 centimeters. This shortcut is useful for mental math, but it is not the exact conversion and should not replace 2.54 when accuracy matters.
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Common conversion mistakes
- Using division instead of multiplication:
12 ÷ 2.54gives approximately 4.72, which is inches from centimeters—not centimeters from inches. - Using 2.5 as the exact factor: 2.5 is only a convenient estimate. The exact factor is 2.54.
- Ignoring feet: Convert every foot to 12 inches before converting the combined measurement.
- Confusing length with area: Square the factor for square inches and cube it for cubic inches.
- Rounding too early: Keep the full result until the final step, especially when converting several measurements or calculating an area.
- Entering units as part of a calculator number: In many calculators, enter the numeric value separately and attach the unit to the result. For example, calculate
5 × 2.54, then label it12.7 cm.
Reference values
These values are useful for common measurements:
| Inches | Centimeters |
|---|---|
| ⅛ | 0.3175 |
| ¼ | 0.635 |
| ½ | 1.27 |
| 1 | 2.54 |
| 2 | 5.08 |
| 5 | 12.7 |
| 10 | 25.4 |
| 12 | 30.48 |
| 24 | 60.96 |
| 36 | 91.44 |
For the exact definition and conversion-factor guidance, see NIST SP 811, Appendix B. NIST’s approximate-conversion guidance is suitable for quick estimates, while exact work should use the 2.54 factor.
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FAQ
What is the exact formula for converting inches to centimeters?
Multiply the inch measurement by 2.54: centimeters = inches × 2.54.
How many centimeters are in one inch?
One inch is exactly 2.54 centimeters.
How many centimeters are in 12 inches?
12 inches equals 30.48 centimeters, calculated as 12 × 2.54.
Do I multiply or divide to convert inches to centimeters?
Multiply by 2.54. Divide by 2.54 when converting centimeters to inches.
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Is 1 inch equal to 2.5 centimeters?
Only approximately. The exact value is 2.54 centimeters; 2.5 is a rough mental-conversion shortcut.
How do I convert square inches to square centimeters?
Square the conversion factor: 1 in² = 6.4516 cm². Do not multiply square inches by 2.54.
The Bottom Line
For a linear measurement, multiply inches by 2.54. Thus, cm = in × 2.54. Use division for the reverse conversion, convert feet-and-inches to total inches first, and square or cube the factor for area or volume.
