The easiest way to get the correct drill diameter size for your tap hole:
Minus the tap pitch from the overall diameter of the tap.
For example Metric course 5mm tap with a 0.8mm pitch = Drill diameter of 4.2mm
Where there is a 0.01mm pitch variation (eg 12mm x 1.75mm Metric Course) go to the next closest drill diameter greater than the pitch.
For example Metric course 12mm tap with a 1.75mm pitch = Drill diameter of 10.2mm