The calculations are pretty simple and once you have the formula it's simple head math to determine what you will need to have in your cellar:
The average pipe holds 2.13 grams of tobacco in my collection but for the sake of argument I rounded the calculations up to 2.5.
A small pipe (group 3) will hold an average of 1.5 grams
A medium pipe (Group 4) will hold an average of 2.0 grams
A large pipe (Group 5) will hold an average of 3 grams
If you have an average mix of small, medium and large pipes in your collection the average smoke will be 2.5 grams.
2.5 grams x 365 days is 912 grams.
912 grams is 32.19 ounces or 1 pound.
SO, 1 pipe a day = 1 pound per year. 2 pipes per day = 2 pounds per year and so on.
The pipe capacities above come from 16 months of (enjoyable) research by weighing every single bowl I smoked prior to drying with a scientific grade scale which has an accuracy to 0.01 grams.
Sorry...... I'm a Stanford Nerd, it's a curse....