How do I convert decimal to inches?
Type a decimal length in inches or feet. The decimal to inches calculator rounds it to the nearest mark on a tape measure, such as 1/16 inch, and shows feet and inches.
- Inches
- 5 3/16 in
5.19 inches is about 5 3/16 in.
- Feet and inches
- 0 ft 5 3/16 in
- Exact inches (decimal)
- 5.19
- Rounding error (in)
- -0.0025
- Millimeters
- 131.83
Inches: 5 3/16 in. 5.19 inches is about 5 3/16 in.
How to calculate
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.
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.
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.
- 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
Each example is checked against the calculator on every build.
- Decimal 5.19, The decimal is in Inches, Nearest 1/16 inch gives Inches 5 3/16 in, Feet and inches 0 ft 5 3/16 in, Rounding error (in) -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)
- Decimal 5.75, The decimal is in Feet, Nearest 1/16 inch gives Inches 69 in, Feet and inches 5 ft 9 in, Exact inches (decimal) 69, Millimeters 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)
- Decimal 0.3125, The decimal is in Inches, Nearest 1/8 inch gives Inches 3/8 in, Rounding error (in) 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)
- Decimal 2.4, The decimal is in Feet, Nearest 1/32 inch gives Inches 28 13/16 in, Feet and inches 2 ft 4 13/16 in, Exact inches (decimal) 28.8, Rounding error (in) 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)
How it works
- Inches. If the decimal is in inches, inches = the decimal. If it is in feet, inches = decimal × 12.
- Round to the nearest mark. For a mark of 1/D inch (D = 2, 4, 8, 16, 32 or 64; 16 by default), n = inches × D rounded to the nearest whole number. A value exactly halfway (a fractional part of 0.5) rounds up.
- Write it. The rounded length is n/D inches, reduced to lowest terms and written as a whole number and a fraction: 83/16 is
5 3/16 in; 72/16 is4 1/2 in; a whole number shows alone (69 in); less than an inch shows only the fraction (3/8 in). - Feet and inches. Whole feet = n ÷ (12 × D), rounded down; the rest is inches, written as in step 3, after
<feet> ft(5 ft 9 in,0 ft 5 3/16 in). - Error = n/D − inches, in inches (positive when rounding went up). Millimeters = inches × 25.4, from the exact length.
The decimal is taken exactly as typed and can be from 0 to 1,000,000,000. All arithmetic is exact.
Output format. The error shows to 6 significant figures, millimeters to 2 decimal places, and the exact inches to 15 significant figures.
Worked examples by hand
5.19 in, nearest 1/16. 5.19 × 16 = 83.04 → 83. 83/16 = 5 3/16 in. Error = 5.1875 − 5.19 = −0.0025 in.
5.75 ft. 5.75 × 12 = 69 in = 5 ft 9 in = 69 × 25.4 = 1,752.6 mm.
0.3125 in, nearest 1/8. 0.3125 × 8 = 2.5, a half, so it rounds up to 3: 3/8 in. Error = 0.375 − 0.3125 = 0.0625 in.
2.4 ft, nearest 1/32. 2.4 × 12 = 28.8 in; 28.8 × 32 = 921.6 → 922. 922/32 = 461/16 = 28 13/16 in = 2 ft 4 13/16 in. Error = 28.8125 − 28.8 = 0.0125 in.
Other questions people ask
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.