M6 × 1 tap drill size

5.00 mm drill — or #9 (0.1960 in) = 79% thread

M6 coarse series, 1 mm pitch. Tap drill Ø = nominal − pitch = 6 − 1 = 5.00 mm (≈77% thread, the standard chart value).

DrillSizeThread %
5.00 mm0.1969 in77%
#9 (inch)0.1960 in / 4.98 mm79%

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.