Fraction to Decimal Chart
Inch fractions from 1/64 to 1" converted to decimal inches and millimetres. Includes common 1/8, 1/16, 1/32 shop fractions and decimal-inch ↔ mm lookup.
Reference
All inch fractions in 64ths up to 1", reduced to lowest terms, with decimal-inch and millimetre equivalents. Machinists, carpenters, and drafters use this for drill selection, plan reading, and converting between fraction-drill and decimal/CAD measurements.
Inch fractions (1/64 → 1") — full table
| Fraction (64ths) | Reduced | Decimal inch | Millimetres |
|---|---|---|---|
| 1/64 | — | 0.015625 | 0.3969 |
| 2/64 | 1/32 | 0.031250 | 0.7937 |
| 3/64 | — | 0.046875 | 1.1906 |
| 4/64 | 1/16 | 0.062500 | 1.5875 |
| 5/64 | — | 0.078125 | 1.9844 |
| 6/64 | 3/32 | 0.093750 | 2.3812 |
| 7/64 | — | 0.109375 | 2.7781 |
| 8/64 | 1/8 | 0.125000 | 3.1750 |
| 9/64 | — | 0.140625 | 3.5719 |
| 10/64 | 5/32 | 0.156250 | 3.9688 |
| 11/64 | — | 0.171875 | 4.3656 |
| 12/64 | 3/16 | 0.187500 | 4.7625 |
| 13/64 | — | 0.203125 | 5.1594 |
| 14/64 | 7/32 | 0.218750 | 5.5562 |
| 15/64 | — | 0.234375 | 5.9531 |
| 16/64 | 1/4 | 0.250000 | 6.3500 |
| 17/64 | — | 0.265625 | 6.7469 |
| 18/64 | 9/32 | 0.281250 | 7.1437 |
| 19/64 | — | 0.296875 | 7.5406 |
| 20/64 | 5/16 | 0.312500 | 7.9375 |
| 21/64 | — | 0.328125 | 8.3344 |
| 22/64 | 11/32 | 0.343750 | 8.7312 |
| 23/64 | — | 0.359375 | 9.1281 |
| 24/64 | 3/8 | 0.375000 | 9.5250 |
| 25/64 | — | 0.390625 | 9.9219 |
| 26/64 | 13/32 | 0.406250 | 10.3187 |
| 27/64 | — | 0.421875 | 10.7156 |
| 28/64 | 7/16 | 0.437500 | 11.1125 |
| 29/64 | — | 0.453125 | 11.5094 |
| 30/64 | 15/32 | 0.468750 | 11.9062 |
| 31/64 | — | 0.484375 | 12.3031 |
| 32/64 | 1/2 | 0.500000 | 12.7000 |
| 33/64 | — | 0.515625 | 13.0969 |
| 34/64 | 17/32 | 0.531250 | 13.4937 |
| 35/64 | — | 0.546875 | 13.8906 |
| 36/64 | 9/16 | 0.562500 | 14.2875 |
| 37/64 | — | 0.578125 | 14.6844 |
| 38/64 | 19/32 | 0.593750 | 15.0812 |
| 39/64 | — | 0.609375 | 15.4781 |
| 40/64 | 5/8 | 0.625000 | 15.8750 |
| 41/64 | — | 0.640625 | 16.2719 |
| 42/64 | 21/32 | 0.656250 | 16.6687 |
| 43/64 | — | 0.671875 | 17.0656 |
| 44/64 | 11/16 | 0.687500 | 17.4625 |
| 45/64 | — | 0.703125 | 17.8594 |
| 46/64 | 23/32 | 0.718750 | 18.2562 |
| 47/64 | — | 0.734375 | 18.6531 |
| 48/64 | 3/4 | 0.750000 | 19.0500 |
| 49/64 | — | 0.765625 | 19.4469 |
| 50/64 | 25/32 | 0.781250 | 19.8438 |
| 51/64 | — | 0.796875 | 20.2406 |
| 52/64 | 13/16 | 0.812500 | 20.6375 |
| 53/64 | — | 0.828125 | 21.0344 |
| 54/64 | 27/32 | 0.843750 | 21.4312 |
| 55/64 | — | 0.859375 | 21.8281 |
| 56/64 | 7/8 | 0.875000 | 22.2250 |
| 57/64 | — | 0.890625 | 22.6219 |
| 58/64 | 29/32 | 0.906250 | 23.0187 |
| 59/64 | — | 0.921875 | 23.4156 |
| 60/64 | 15/16 | 0.937500 | 23.8125 |
| 61/64 | — | 0.953125 | 24.2094 |
| 62/64 | 31/32 | 0.968750 | 24.6062 |
| 63/64 | — | 0.984375 | 25.0031 |
| 64/64 | 1/1 | 1.000000 | 25.4000 |
Common shop fractions
| Fraction | Decimal inch | mm |
|---|---|---|
| 1/16 | 0.0625 | 1.5875 |
| 1/8 | 0.1250 | 3.1750 |
| 3/16 | 0.1875 | 4.7625 |
| 1/4 | 0.2500 | 6.3500 |
| 5/16 | 0.3125 | 7.9375 |
| 3/8 | 0.3750 | 9.5250 |
| 7/16 | 0.4375 | 11.1125 |
| 1/2 | 0.5000 | 12.7000 |
| 9/16 | 0.5625 | 14.2875 |
| 5/8 | 0.6250 | 15.8750 |
| 11/16 | 0.6875 | 17.4625 |
| 3/4 | 0.7500 | 19.0500 |
| 13/16 | 0.8125 | 20.6375 |
| 7/8 | 0.8750 | 22.2250 |
| 15/16 | 0.9375 | 23.8125 |
| 1 | 1.0000 | 25.4000 |
Decimal inch → mm (reverse look-up)
| Decimal in | mm | Nearest fraction |
|---|---|---|
| 0.010 | 0.2540 | ≈ 0 (thou) |
| 0.031 | 0.7937 | 1/32 |
| 0.040 | 1.0160 | ≈ 3/64 |
| 0.050 | 1.2700 | ≈ 1/16 - 3/64 |
| 0.063 | 1.6002 | 1/16 |
| 0.100 | 2.5400 | 7/64 (.109) |
| 0.125 | 3.1750 | 1/8 |
| 0.200 | 5.0800 | 13/64 (.203) |
| 0.250 | 6.3500 | 1/4 |
| 0.375 | 9.5250 | 3/8 |
| 0.500 | 12.7000 | 1/2 |
| 0.625 | 15.8750 | 5/8 |
| 0.750 | 19.0500 | 3/4 |
| 0.875 | 22.2250 | 7/8 |
| 1.000 | 25.4000 | 1 |
Commonly rounded conversions
- 1 inch
- = 25.4 mm (exact by international agreement, 1959)
- 1 foot
- = 12 in = 304.8 mm
- 1 yard
- = 36 in = 914.4 mm
- 1 mil / thou
- = 0.001 in = 0.0254 mm = 25.4 µm
- 1 mm
- ≈ 0.03937 in = 39.37 thou
- 1 cm
- = 0.3937 in
- 1 meter
- ≈ 39.3701 in = 3.2808 ft
Tips
- To convert fraction → decimal: divide top by bottom. 5/16 = 5 ÷ 16 = 0.3125.
- To convert decimal → fraction of an inch: multiply by 64, round to whole number, reduce. 0.42" × 64 = 26.88 → 27/64".
- To convert inch → mm: multiply by 25.4. Exact — never rounded in engineering.
- To convert mm → inch: multiply by 0.0393701 (or divide by 25.4). 15 mm ÷ 25.4 = 0.5906".
- Never mix significant figures: if your measurement is to 1/64" (0.0156" = 0.4 mm), don't report a 0.001 mm result.
- Shop rules of thumb: 1 mm ≈ 1/25 in or 40 mm ≈ 1-1/2 in for quick estimates.
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