CM to Inches Fraction Calculator
Turn a centimetre measurement into the nearest fraction of an inch you can find on a tape measure, and see how close the fraction is.
More cm and inch tools
How to use the CM to Inches Fraction Calculator
- Enter the measurement in centimetres.
- Choose the precision — 1/16 inch for most tape measures.
- Read the fraction, the exact decimal inches and the rounding error.
How it works
The centimetres are divided by 2.54 to get decimal inches, multiplied by the chosen denominator, rounded to a whole number and simplified. The rounding error is the difference between that fraction and the exact size.
How to convert cm to an inch fraction
- Convert to decimal inches: divide by 2.54. 7 cm ÷ 2.54 = 2.756″.
- Keep the whole inches (2) and multiply the decimal part by 16: 0.756 × 16 = 12.1.
- Round to 12 and write it over 16: 12/16.
- Simplify: 12/16 = 3/4, so 7 cm ≈ 2 3/4″.
The calculator above does this for any value and lets you choose 1/8, 1/16, 1/32 or 1/64 inch.
CM to inch fractions table
| Centimetres | Decimal inches | Nearest 1/16″ | Error at 1/16″ | Nearest 1/32″ |
|---|---|---|---|---|
| 0.5 cm | 0.1969″ | 3/16″ | −0.2 mm | 3/16″ |
| 1 cm | 0.3937″ | 3/8″ | −0.5 mm | 13/32″ |
| 1.5 cm | 0.5906″ | 9/16″ | −0.7 mm | 19/32″ |
| 2 cm | 0.7874″ | 13/16″ | +0.6 mm | 25/32″ |
| 2.5 cm | 0.9843″ | 1″ | +0.4 mm | 31/32″ |
| 3 cm | 1.1811″ | 1 3/16″ | +0.2 mm | 1 3/16″ |
| 4 cm | 1.5748″ | 1 9/16″ | −0.3 mm | 1 9/16″ |
| 5 cm | 1.9685″ | 1 15/16″ | −0.8 mm | 1 31/32″ |
| 6 cm | 2.3622″ | 2 3/8″ | +0.3 mm | 2 3/8″ |
| 7 cm | 2.7559″ | 2 3/4″ | −0.2 mm | 2 3/4″ |
| 8 cm | 3.1496″ | 3 1/8″ | −0.6 mm | 3 5/32″ |
| 9 cm | 3.5433″ | 3 9/16″ | +0.5 mm | 3 17/32″ |
| 10 cm | 3.937″ | 3 15/16″ | +0 mm | 3 15/16″ |
| 12 cm | 4.7244″ | 4 3/4″ | +0.7 mm | 4 23/32″ |
| 15 cm | 5.9055″ | 5 7/8″ | −0.8 mm | 5 29/32″ |
| 20 cm | 7.874″ | 7 7/8″ | +0 mm | 7 7/8″ |
| 25 cm | 9.8425″ | 9 13/16″ | −0.8 mm | 9 27/32″ |
| 30 cm | 11.811″ | 11 13/16″ | +0 mm | 11 13/16″ |
The error column shows how far the 1/16″ mark is from the true size. Errors under about half a millimetre are invisible in sewing and carpentry; for precision work use the decimal value from the cm to inches converter.
Where inch fractions are used
American patterns, woodworking plans, picture frames and hardware are sized in fractions of an inch, so a metric measurement often has to be turned into a fraction you can find on a tape. Quilting and sewing usually work to 1/8″, carpentry to 1/16″, and cabinet making to 1/32″. For millimetre measurements, the mm to inches fraction calculator does the same job; for any decimal inch, use the decimal to fraction inches calculator.
Frequently asked questions
What is 10 cm as an inch fraction?
About 3 15/16″ (exact 3.937″).
What is 5 cm in inches as a fraction?
About 1 15/16″ (exact 1.969″).
What is 1 cm as a fraction of an inch?
About 3/8″ (exact 0.394″), or 25/64″ to the nearest 1/64.
Why is the fraction not exact?
Most centimetre values fall between inch-fraction marks, so the nearest mark is shown with its error.