base 7 is a positional numeral system with seven as its base. It uses 7 different digits for representing numbers. The digits for base 7 could be 0, 1, 2, 3, 4, 5, and 6.

conversion table

base 7	base 5	base 7	base 5
1	≈ 1	14	≈ 21
2	≈ 2	15	≈ 22
3	≈ 3	16	≈ 23
4	≈ 4	20	≈ 24
5	≈ 10	21	≈ 30
6	≈ 11	22	≈ 31
10	≈ 12	23	≈ 32
11	≈ 13	24	≈ 33
12	≈ 14	25	≈ 34
13	≈ 20	26	≈ 40