| Decimal Number | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| Octal Number | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 20 | 21 | 22 | 23 | 24 |
The octal system is radix-8, this system uses the numerals 0-7. This system is a great thing to know. When you're using the octal system, you can at a glance, know what number you are looking at in binary. Every three binary columns are an octal number. Let's look at a table:
| Binary Number | Decimal Equivalent | Octal Equivalent |
| 101101 | 32 + 8 + 4 + 1 = 4510 | 558 = 5 * 810 + 5 = 4510 |
| 111100 | 32 + 16 + 8 + 4 = 6010 | 748 = 7 * 810 + 4 = 4510 |
Every three binary columns can go from 0 - 7 in magnitude. This means you are either staring at a 1's column, a 2's column, or a 4's column. Every set of three to the left over you go, you add a * 8. (Cn).
Where: c= columns to shift over, and n = power of set, with the exception of the first set where n = 0 (the 1's set)
/ ∞ \
| ∑ (c + 3) | ÷ 3 = n
\ c = 3 /
So let's break it down in another table:
| Binary Number | Octal Sets | Conversion Equivalent |
| 10110101 | 10 110 101 | 2 * 8210 + 6 * 8110 + 5 * 8010 = 18110 |