There is a simple formula to determine how may Boveda Packs you require.

You will need one Pack for the Humidor itself and then one pack for every 50 cigars of CAPACITY. So if you have a humidor that holds 40 cigars, use 2 packs. If your box holds 75 cigars, use 3 packs. 100 cigars, 3 packs. You get the picture.

The same formula holds true when starting your humidor off with the seasoning packs.