Decimal Inches to Fraction Converter
Type decimal inches such as 0.3125 or 2.83 and get the nearest tape-measure fraction, from 1/2″ to 1/64″, with the rounding error and a diagram showing exactly where it falls between the marks. Switch direction to turn a fraction like 1 3/8 back into a decimal.
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Examples: 5/16, 1 3/8, 2-7/64, 3 1/2"
How to use the Decimal Inches to Fraction Converter
- Type the decimal inches, e.g. 0.3125, or tap an example.
- Choose the precision: 1/16″ for a standard tape, 1/32″ or 1/64″ for finer work.
- Pick rounding: nearest, or down/up when a part must fit or clear.
- Read the fraction, the error and the tape diagram showing where it lands.
- Need the reverse? Choose Fraction → decimal and type a fraction such as 1 3/8.
How to turn decimal inches into a fraction
Tape measures and rulers are divided into halves, quarters, eighths and sixteenths (some into 32nds and 64ths), so a decimal like 0.47″ from a drawing, caliper or spreadsheet has to be rounded to the nearest mark. The method:
- Keep the whole inches aside. In 2.83″, the whole part is 2 and the decimal part is 0.83.
- Multiply the decimal by the denominator of your precision. For sixteenths: 0.83 × 16 = 13.28.
- Round to a whole number: 13.28 → 13, giving 13/16. (Round down or up instead if a part must fit or must clear.)
- Simplify if the top is even: 12/16 → 3/4, 8/16 → 1/2. 13/16 is already in lowest terms.
- Put it back together: 2.83″ ≈ 2 13/16″, which is 2.8125″, so the mark is 0.0175″ (0.44 mm) short.
Going the other way is just division: 1 3/8″ = 1 + 3 ÷ 8 = 1.375″. Switch the tool to Fraction → decimal and type fractions like 5/16, 1 3/8 or 2-7/64.
Fraction to decimal inch chart (1/64″ steps)
| Fraction | Decimal | Fraction | Decimal | Fraction | Decimal | Fraction | Decimal |
|---|---|---|---|---|---|---|---|
| 1/64″ | 0.015625 | 17/64″ | 0.265625 | 33/64″ | 0.515625 | 49/64″ | 0.765625 |
| 1/32″ | 0.031250 | 9/32″ | 0.281250 | 17/32″ | 0.531250 | 25/32″ | 0.781250 |
| 3/64″ | 0.046875 | 19/64″ | 0.296875 | 35/64″ | 0.546875 | 51/64″ | 0.796875 |
| 1/16″ | 0.062500 | 5/16″ | 0.312500 | 9/16″ | 0.562500 | 13/16″ | 0.812500 |
| 5/64″ | 0.078125 | 21/64″ | 0.328125 | 37/64″ | 0.578125 | 53/64″ | 0.828125 |
| 3/32″ | 0.093750 | 11/32″ | 0.343750 | 19/32″ | 0.593750 | 27/32″ | 0.843750 |
| 7/64″ | 0.109375 | 23/64″ | 0.359375 | 39/64″ | 0.609375 | 55/64″ | 0.859375 |
| 1/8″ | 0.125000 | 3/8″ | 0.375000 | 5/8″ | 0.625000 | 7/8″ | 0.875000 |
| 9/64″ | 0.140625 | 25/64″ | 0.390625 | 41/64″ | 0.640625 | 57/64″ | 0.890625 |
| 5/32″ | 0.156250 | 13/32″ | 0.406250 | 21/32″ | 0.656250 | 29/32″ | 0.906250 |
| 11/64″ | 0.171875 | 27/64″ | 0.421875 | 43/64″ | 0.671875 | 59/64″ | 0.921875 |
| 3/16″ | 0.187500 | 7/16″ | 0.437500 | 11/16″ | 0.687500 | 15/16″ | 0.937500 |
| 13/64″ | 0.203125 | 29/64″ | 0.453125 | 45/64″ | 0.703125 | 61/64″ | 0.953125 |
| 7/32″ | 0.218750 | 15/32″ | 0.468750 | 23/32″ | 0.718750 | 31/32″ | 0.968750 |
| 15/64″ | 0.234375 | 31/64″ | 0.484375 | 47/64″ | 0.734375 | 63/64″ | 0.984375 |
| 1/4″ | 0.250000 | 1/2″ | 0.500000 | 3/4″ | 0.750000 | 1″ | 1.000000 |
Reading the marks on a tape measure
- The longest lines are whole inches, then the 1/2″ mark, then 1/4″, 1/8″ and the shortest 1/16″ ticks. The diagram in the tool follows the same pattern down to 1/32″.
- Count sixteenths from the last whole inch: the 5th short tick after 3″ is 3 5/16″.
- Decimals worth memorising: 0.0625 = 1/16, 0.125 = 1/8, 0.1875 = 3/16, 0.25 = 1/4, 0.375 = 3/8, 0.5 = 1/2, 0.625 = 5/8, 0.75 = 3/4, 0.875 = 7/8.
- At 1/16″ precision the largest possible rounding error is 1/32″ (about 0.79 mm); at 1/64″ it is 1/128″ (about 0.2 mm).
Frequently asked questions
What is 0.3125 inches as a fraction?
0.3125 inches is exactly 5/16 inch: 0.3125 × 16 = 5. No rounding is needed.
How do I convert decimal inches to the nearest 1/16?
Multiply the decimal part by 16, round to the nearest whole number and put it over 16, then simplify. For 0.47: 0.47 × 16 = 7.52 → 8/16 = 1/2 inch.
What is 0.1 inch as a fraction?
0.1 × 32 = 3.2, so 0.1 inch is about 3/32 inch (0.09375) at 1/32 precision; 1/64 precision gives the same 3/32. At 1/16 precision it rounds to 2/16 = 1/8 inch (0.125).
How do I convert a fraction of an inch to a decimal?
Divide the top number by the bottom number and add any whole inches. 1 3/8″ = 1 + 3 ÷ 8 = 1.375 inches, or 34.925 mm.
What is the biggest error when rounding to 1/16 inch?
Half of 1/16 inch, which is 1/32 inch (0.03125 in or about 0.79 mm). Rounding to 1/64 inch keeps the error under 1/128 inch (about 0.2 mm).
Should I round up or down?
Round to the nearest mark for general measuring. Round down when a piece must fit inside a space, and round up when it must cover or clear a size, such as a hole that a pin has to pass through.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.