M3 × 0.5 tap drill size

2.50 mm drill — or #40 (0.0980 in) = 79% thread

M3 coarse series, 0.5 mm pitch. Tap drill Ø = nominal − pitch = 3 − 0.5 = 2.50 mm (≈77% thread, the standard chart value).

Rounding to your nearest stock drill moves the thread percentage only a few points. Cut taps only — roll-form taps need a larger hole. Verify before you cut.

Need a different thread percentage? Open the tap drill calculator · Metric tap chart · All calculators