M22 × 1.5 tap drill size

20.50 mm drill — or 13/16 (0.8125 in) = 70% thread

M22 fine series, 1.5 mm pitch. Tap drill Ø = nominal − pitch = 22 − 1.5 = 20.50 mm (≈77% thread, the standard chart value).

DrillSizeThread %
20.50 mm0.8071 in77%
13/16 (inch)0.8125 in / 20.64 mm70%

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.