# How do I convert decimal to inches?

Converts decimal inches or decimal feet to inches and fractions of an inch, to the nearest 1/16 or any mark from 1/2 to 1/64, with feet and inches.

- Page: https://www.acalculator.org/convert/decimal-to-inches
- JSON spec: https://www.acalculator.org/convert/decimal-to-inches.json
- Version: 5a01c59c035d

## Default answer

Example with the default inputs (Decimal 5.19, The decimal is in Inches, Nearest 1/16 inch): 5.19 inches is about 5 3/16 in.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| d | Decimal | The decimal length, for example 5.19. |
| u | The decimal is in | Inches (5.19 in) or feet (5.75 ft). |
| n | Nearest | The smallest mark to round to: 1/16 inch on most tape measures. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| inches | Inches | The length in whole inches and a fraction, rounded to the nearest mark. |
| feetInches | Feet and inches | The rounded length as whole feet and inches. |
| exact | Exact inches (decimal) | The length in inches before rounding. |
| error | Rounding error (in) | The rounded length minus the exact length, in inches. |
| mm | Millimeters | The exact length in millimeters (1 in = 25.4 mm). |

## Method

Inches = the decimal (× 12 when it is in feet). Rounded inches = round(inches × D) ÷ D for the mark 1/D, halves rounded up, written as a whole number and a fraction in lowest terms.

## Assumptions

- The decimal is taken exactly as typed; 1 ft = 12 in and 1 in = 25.4 mm exactly.
- A length exactly halfway between two marks rounds up to the larger mark.

## Worked examples

1. d = 5.19, u = in, n = 16 gives inches = 5 3/16 in, feetInches = 0 ft 5 3/16 in, error = -0.0025. Source: OpenStax, Prealgebra 2e, §5.1 Decimals (a decimal as a fraction, rounding), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-10-05).
2. d = 5.75, u = ft, n = 16 gives inches = 69 in, feetInches = 5 ft 9 in, exact = 69, mm = 1,752.6. Source: NIST SP 811, Appendix B.8 (1 ft = 12 in = 0.3048 m; 1 in = 2.54 cm), https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8 (retrieved 2026-10-05).
3. d = 0.3125, u = in, n = 8 gives inches = 3/8 in, error = 0.0625. Source: OpenStax, Prealgebra 2e, §5.1 Decimals (a decimal as a fraction, rounding), https://openstax.org/books/prealgebra-2e/pages/5-1-decimals (retrieved 2026-10-05).
4. d = 2.4, u = ft, n = 32 gives inches = 28 13/16 in, feetInches = 2 ft 4 13/16 in, exact = 28.8, error = 0.0125. Source: NIST SP 811, Appendix B.8 (1 ft = 12 in = 0.3048 m; 1 in = 2.54 cm), https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8 (retrieved 2026-10-05).

## FAQ

### How do I convert decimal inches to a fraction?

Multiply the decimal part by the marks per inch, round, and put it over that number. For 5.19 in to the nearest 1/16: 0.19 × 16 = 3.04, which rounds to 3, so 5 3/16 in.

### How do I convert decimal feet to inches?

Multiply by 12. 5.75 ft × 12 = 69 in, which is 5 ft 9 in.

### Why the nearest 1/16 inch?

Most tape measures mark sixteenths of an inch. Pick 1/32 or 1/64 for finer work, or 1/8 or 1/4 for rough work.

### What happens exactly halfway between two marks?

It rounds up. 0.3125 in is 5/16, halfway between 2/8 and 3/8, so to the nearest 1/8 it is 3/8 in.

### How far off is the rounded value?

At most half a mark: 1/32 inch (0.03125 in) when you round to sixteenths. The page shows the exact error.

### What is 0.1 inch as a fraction?

0.1 × 16 = 1.6, which rounds to 2, so it is about 2/16 = 1/8 in. As an exact fraction, 0.1 is 1/10.

## Sources

- OpenStax, Prealgebra 2e, §5.1 Decimals: a decimal as a fraction and rounding to a place. CC BY 4.0. Retrieved 2026-10-05. https://openstax.org/books/prealgebra-2e/pages/5-1-decimals
- NIST Special Publication 811, Appendix B.8: 1 ft = 0.3048 m and 1 in = 2.54 cm exactly, so 1 ft = 12 in. Retrieved 2026-10-05. https://www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors/nist-guide-si-appendix-b8