M2.5 × 0.45 tap drill size

2.05 mm drill — or #46 (0.0810 in) = 76% thread

M2.5 coarse series, 0.45 mm pitch. Tap drill Ø = nominal − pitch = 2.5 − 0.45 = 2.05 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