M8 × 1.25 tap drill size

6.75 mm drill — or 17/64 (0.2656 in) = 77% thread

M8 coarse series, 1.25 mm pitch. Tap drill Ø = nominal − pitch = 8 − 1.25 = 6.75 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