Tables for using a d120 as a dn
The d120 can be used as a dn, where n is any proper factor of 120. For the standard seven-dice polyset, a d120 is the ideal "multi-die", as 120 is the least common multiple of 4, 6, 8, 10, 12, and 20. Odd numbers like 3, 5, and 15 are also of particular note, as there are no isohedra with an odd number of faces. In addition, there are no d40's on the market to the best of our knowledge.
Note that a very large die like the d120 is likely to be less fair than standard dice due to the small angles between adjacent faces, which make a large die more sensitive to manufacturing inaccuracies. So using the d120 as a d6, e.g., may be entertaining, but a regular d6 will probably perform better as a d6.
The tables below provide values for the standard dn for a roll of the d120. Note that the d120 can also be used as a d2; simply consider any odd number to represent a 1 and any even number to represent a 2. Click here for a printer-friendly pdf document containing these tables.