Decimal to Octal
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Quick answer
To convert decimal to octal, divide by 8 repeatedly and read the remainders from last to first — for example 100 → 144 (octal). TryDevSnip's converter does it instantly and exactly, all in your browser.
Decimal to octal chart
| Decimal | Octal |
|---|---|
| 8 | 10 |
| 15 | 17 |
| 16 | 20 |
| 64 | 100 |
| 100 | 144 |
| 256 | 400 |
| 511 | 777 |
| 512 | 1000 |
Related: octal to decimal · decimal to hex · all bases
Worked example: 64
Every positional number system works the same way — each digit is multiplied by the base raised to its position, counting from zero on the right. For 64 in decimal:
| Digit | Place | Weight | Contribution |
|---|---|---|---|
| 6 | 101 | 10 | 60 |
| 4 | 100 | 1 | 4 |
| Total (decimal) | 64 | ||
Written in octal that is 0o100.
Quick reference
| Decimal | decimal | octal |
|---|---|---|
| 1 | 1 | 1 |
| 2 | 2 | 2 |
| 4 | 4 | 4 |
| 8 | 8 | 10 |
| 10 | 10 | 12 |
| 16 | 16 | 20 |
| 32 | 32 | 40 |
| 64 | 64 | 100 |
| 100 | 100 | 144 |
| 128 | 128 | 200 |
| 255 | 255 | 377 |
| 256 | 256 | 400 |
Things that trip people up
- Prefixes are notation, not value.
0b1010,0o12,0xAand10can all denote the same quantity. Strip the prefix before parsing, or tell the parser which base you meant. - Leading zeros can change the base. In several languages a leading
0historically meant octal, so010parsed as 8 rather than 10. Passing an explicit radix avoids the whole class of bug. - Hex letters are case-insensitive.
0xffand0xFFare the same number; only presentation differs. - Grouping is for humans. Binary is usually read in nibbles of four (
1111 1111) because each nibble maps to exactly one hex digit — which is why hex is the usual shorthand for binary data.
Frequently asked questions
How do I convert decimal to octal?
Divide the number by 8 repeatedly and read the remainders from last to first. For example 100 ÷ 8 → 144 (octal). Or paste it into the converter and read the octal instantly.
What is 8 in octal?
8 (decimal) is 10 in octal — base 8 rolls over after 7, so eight is written as 10.
Where is octal used?
Most commonly in Unix file permissions (chmod), where three permission bits map to one octal digit — e.g. rwxr-xr-x is 755.
Is my input uploaded?
No. TryDevSnip converts locally in your browser. Nothing you type is uploaded to our servers for processing.