M24 × 3 tap drill size

21.00 mm drill — or 53/64 (0.8281 in) = 76% thread

M24 coarse series, 3 mm pitch. Tap drill Ø = nominal − pitch = 24 − 3 = 21.00 mm (≈77% thread, the standard chart value).

DrillSizeThread %
21.00 mm0.8268 in77%
53/64 (inch)0.8281 in / 21.03 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.