Fraction to decimal to millimeter chart
The classic shop-wall lookup: every 64th of an inch up to one inch, then sixteenths up to two inches, with exact decimals throughout. Print it at 100% scale and tape it inside a cabinet door.
| Fraction | Decimal (in) | mm | Fraction | Decimal (in) | mm |
|---|---|---|---|---|---|
| 1/64" | 0.0156 | 0.3969 | 41/64" | 0.6406 | 16.2719 |
| 1/32" | 0.0313 | 0.7937 | 21/32" | 0.6563 | 16.6687 |
| 3/64" | 0.0469 | 1.1906 | 43/64" | 0.6719 | 17.0656 |
| 1/16" | 0.0625 | 1.5875 | 11/16" | 0.6875 | 17.4625 |
| 5/64" | 0.0781 | 1.9844 | 45/64" | 0.7031 | 17.8594 |
| 3/32" | 0.0938 | 2.3812 | 23/32" | 0.7188 | 18.2562 |
| 7/64" | 0.1094 | 2.7781 | 47/64" | 0.7344 | 18.6531 |
| 1/8" | 0.1250 | 3.1750 | 3/4" | 0.7500 | 19.0500 |
| 9/64" | 0.1406 | 3.5719 | 49/64" | 0.7656 | 19.4469 |
| 5/32" | 0.1563 | 3.9688 | 25/32" | 0.7813 | 19.8438 |
| 11/64" | 0.1719 | 4.3656 | 51/64" | 0.7969 | 20.2406 |
| 3/16" | 0.1875 | 4.7625 | 13/16" | 0.8125 | 20.6375 |
| 13/64" | 0.2031 | 5.1594 | 53/64" | 0.8281 | 21.0344 |
| 7/32" | 0.2188 | 5.5562 | 27/32" | 0.8438 | 21.4312 |
| 15/64" | 0.2344 | 5.9531 | 55/64" | 0.8594 | 21.8281 |
| 1/4" | 0.2500 | 6.3500 | 7/8" | 0.8750 | 22.2250 |
| 17/64" | 0.2656 | 6.7469 | 57/64" | 0.8906 | 22.6219 |
| 9/32" | 0.2813 | 7.1437 | 29/32" | 0.9063 | 23.0187 |
| 19/64" | 0.2969 | 7.5406 | 59/64" | 0.9219 | 23.4156 |
| 5/16" | 0.3125 | 7.9375 | 15/16" | 0.9375 | 23.8125 |
| 21/64" | 0.3281 | 8.3344 | 61/64" | 0.9531 | 24.2094 |
| 11/32" | 0.3438 | 8.7312 | 31/32" | 0.9688 | 24.6062 |
| 23/64" | 0.3594 | 9.1281 | 63/64" | 0.9844 | 25.0031 |
| 3/8" | 0.3750 | 9.5250 | 1" | 1.0000 | 25.4000 |
| 25/64" | 0.3906 | 9.9219 | 1 1/16" | 1.0625 | 26.9875 |
| 13/32" | 0.4063 | 10.3187 | 1 1/8" | 1.1250 | 28.5750 |
| 27/64" | 0.4219 | 10.7156 | 1 3/16" | 1.1875 | 30.1625 |
| 7/16" | 0.4375 | 11.1125 | 1 1/4" | 1.2500 | 31.7500 |
| 29/64" | 0.4531 | 11.5094 | 1 5/16" | 1.3125 | 33.3375 |
| 15/32" | 0.4688 | 11.9063 | 1 3/8" | 1.3750 | 34.9250 |
| 31/64" | 0.4844 | 12.3031 | 1 7/16" | 1.4375 | 36.5125 |
| 1/2" | 0.5000 | 12.7000 | 1 1/2" | 1.5000 | 38.1000 |
| 33/64" | 0.5156 | 13.0969 | 1 9/16" | 1.5625 | 39.6875 |
| 17/32" | 0.5313 | 13.4937 | 1 5/8" | 1.6250 | 41.2750 |
| 35/64" | 0.5469 | 13.8906 | 1 11/16" | 1.6875 | 42.8625 |
| 9/16" | 0.5625 | 14.2875 | 1 3/4" | 1.7500 | 44.4500 |
| 37/64" | 0.5781 | 14.6844 | 1 13/16" | 1.8125 | 46.0375 |
| 19/32" | 0.5938 | 15.0812 | 1 7/8" | 1.8750 | 47.6250 |
| 39/64" | 0.6094 | 15.4781 | 1 15/16" | 1.9375 | 49.2125 |
| 5/8" | 0.6250 | 15.8750 | 2" | 2.0000 | 50.8000 |
Converting any fraction yourself
Divide top by bottom to get decimal inches, then multiply by 25.4:
mm = (numerator ÷ denominator) × 25.4
Example: 11/32" → 11 ÷ 32 = 0.34375" → 0.34375 × 25.4 = 8.73125 mm. For whole numbers and decimals rather than fractions, use the regular inches-to-millimeters converter.
Frequently asked questions
Why does the millimeter column matter so much for fractions?
Because 1" is exactly 25.4 mm by international agreement since 1959, every fraction converts exactly. A 3/8" bit is exactly 9.525 mm — which is why metric and inch fasteners never quite interchange.
How do I read "thousandths of an inch" against this table?
The decimal column is the same number in thousandths. 0.625" is 625 thou, or 5/8". For very small measurements, our thousandths-to-millimeters converter handles values below this chart's range.
Which fractions are worth memorizing?
The eighths: 1/8" = 0.125", 1/4" = 0.250", 3/8" = 0.375", 1/2" = 0.500", 5/8" = 0.625", 3/4" = 0.750", 7/8" = 0.875". Every other fraction on a tape is halfway between two of them.
All values computed exactly from 1 inch = 25.4 mm (NIST SP 811); no rounding beyond display.