Number Bases
Base eight (octal)
A number system using the digits 0 to 7, where each place is a power of eight.
| English | Base eight (octal) |
|---|---|
| Bahasa Melayu | Asas lapan |
| 中文 | 八进制 |
How it is used
To convert 57 base eight to base ten, use powers of eight: 5×8 + 7 = 40 + 7 = 47. So 57₈ = 47₁₀.
Where it shows up in SPM
Base eight is one of the three named bases in the Number Bases chapter (Form 5). Paper 1 tests conversions between base eight and base ten or binary; Paper 2 may route a conversion through binary, since three binary digits make exactly one octal digit.
Don't confuse it with
Open the chapter: Number Bases →
Frequently asked questions
Why is base eight called octal?
'Oct' means eight, so octal is simply the base-eight system that uses the digits 0 to 7. In SPM you may see either name, but the working is the same: each column is a power of eight.
How do I convert binary straight to base eight?
Group the binary digits into threes from the right, then read each group as an octal digit. For 101110₂, group as 101 110, which is 5 and 6, giving 56₈.
Add leading zeros if the last group is short.