Convert dowel pin diameters between inch fractions, decimal inches, and millimeters. Pick a standard pin, enter a measured diameter from calipers, and compare nearby inch and metric sizes for jigs, fixtures, tooling, hinges, and machine repairs.
Choose a standard dowel pin diameter or enter your measured pin size.
Enter a size to convert.
Use the chart for quick inch-to-metric comparisons. For press fits, slip fits, and hardened ground dowel pins, the hole size and tolerance should come from your drawing, reamer chart, or pin supplier.
| Pin size | Decimal inch | Millimeters | Nearest alternate | Typical use |
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Dowel pins are often used for accurate location, not just fastening. A 6 mm dowel pin is close to 1/4 inch, but it is not the same: 6 mm is about 0.2362 inch, while 1/4 inch is 0.2500 inch. That difference is enough to matter in a reamed hole or alignment fixture.
No. A 6 mm dowel pin is about 0.2362 inch. A 1/4 inch dowel pin is 0.2500 inch, or 6.35 mm.
A 3/8 inch dowel pin is 0.3750 inch, which converts to 9.53 mm.
Not blindly. Dowel pins can need a press fit, transition fit, or slip fit depending on the job. Use the converter for diameter comparison, then use the specified hole tolerance for the actual part.