M12 × 1.75 tap drill size

10.25 mm drill — or Y (0.4040 in) = 76% thread

M12 coarse series, 1.75 mm pitch. Tap drill Ø = nominal − pitch = 12 − 1.75 = 10.25 mm (≈77% thread, the standard chart value).

DrillSizeThread %
10.25 mm0.4035 in77%
Y (inch)0.4040 in / 10.26 mm76%

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.