Have you ever wondered what the optimal grit progression is if you are aiming for a 25% increase at every step? Or a 50% increase? Wonder no more! This spreadsheet will calculate it all for you:

Sandpaper grit progression calculator

By the way, here are some precalculated progressions, starting at 40 grit. I picked the available grits from the Festool Granat line which has a pretty complete set of grits. The 25% and 33% are probably excessive - I would personally use a 50% progression or something around there.

Step25% Progression33% Progression50% Progression75% Progression100% Progression
Step 14040404040
Step 26060606080
Step 3808080100150
Step 4100100120150280
Step 5120120180240500
Step 61501502404001000
Step 71801803606001500
Step 82202405001000
Step 92403206001500
Step 10280400800
Step 113205001200
Step 124006001500
Step 13500800
Step 146001000
Step 158001200
Step 1610001500
Step 171200
Step 181500