End Mill Diameter Chart

Standard end mill diameters in fractional inch and metric, with decimal and millimeter equivalents. Use it to match a cutter to a feature and to convert between systems.

Fractional inch

Diameter Decimal (in) mm
1/16 in 0.0625 1.59
3/32 in 0.0938 2.38
1/8 in 0.1250 3.17
5/32 in 0.1563 3.97
3/16 in 0.1875 4.76
1/4 in 0.2500 6.35
5/16 in 0.3125 7.94
3/8 in 0.3750 9.52
1/2 in 0.5000 12.70
5/8 in 0.6250 15.88
3/4 in 0.7500 19.05
1 in 1.0000 25.40

Metric

Diameter Inch (in)
1 mm 0.0394
2 mm 0.0787
3 mm 0.1181
4 mm 0.1575
5 mm 0.1969
6 mm 0.2362
8 mm 0.3150
10 mm 0.3937
12 mm 0.4724

The most common sizes; many shops stock these plus reduced-shank and undersize cutters. Convert any size with the Unit Conversion Calculator.

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The calculators and tools on Formula Factory are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. Formula Factory makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.