Let's take a Dunhill GROUP 4 size pipe (14 of my random pipes are within +- 10% of that size so either my collection is biased or many pipes are about a Group 4).
A group 4 measures (inside dimensions)
- Diameter = 20mm, thus radius=10mm
- Height = 37mm
We can use these dimensions to calculate the volume of the tobacco chamber V1= pi * radius * radius * height = pi * 10 * 10 * 37 = 11,623 cubic mm
I usually pack the tobacco about as tight as I find it in a Dunhill Nightcap tin.
That tin measures:
- Diameter: 100mm, thus radius = 50mm
- Height: 27mm
and holds 50g of tobacco, thus those 50g of tobacco are kept inside a volume of V2 = pi * 104 * 104 * 27 = 917,445 cubic mm
So we know that at the packing grade of about Dunhill Nightcap we have a weight of 0.000235 grams of pipe tobacco per cubic mm (divide 50g by V2).
In return, we now know that a group 4 bowl at that packing density would use up V1 * 0.000235 = 2.74g grams of our tobacco.
There are 28.34 grams in 1 oz, therefore 1 oz will fill 10 full group 4 bowls, and one group 2 bowl.