Use the 6, 8, 10, and 12 sided dice.
1. 1/12=8.33%
2. 1/10=10%
3. 1/8=12.5%
4. 1/6=16.67%
5. 2/10=20%
6. 2/8=25%
7. 3/10=30%
8. 2/6=33.33%
9. 3/8=37.5%
10. 4/10=40%
11. 5/12=41.67%
12. 3/6=50%
13. 7/12=58.33
14. 6/10=60%
15. 5/8=62.5
16. 4/6=66.67%
17. 7/10=70%
18. 6/8=75%
19. 8/10=80%
20. 5/6=83.33%
21. 7/8=87.5%
22. 9/10=90%
23. 11/12=91.67%
This will give you 23 different percentages to work with.
If you are worry about the 12 sided dice rolling to much, Young Grasshopper is promoting a unique 8 sided dice that rolls more than a 12 sided dice on his Grasshopper’s 8 Sided System (G40) posting.