Decimal to Octal Converter
Convert decimal numbers to octal format
Tip: Enter a decimal number (0-9 only). The conversion happens in real-time.
Runs in your browserDecimal Octal
Decimal to octal, step by step
Convert decimal to octal
Enter a decimal number and the octal result is shown as you type. Long results also appear in groups of three digits, and the window bar gives the bit length.
Octal is base 8 and uses only the digits 0 to 7. You meet it in Unix file permissions, where 755 and 644 are octal numbers, and in code as a literal with a 0o prefix, or a leading 0 in C.
How to convert decimal to octal by hand
Divide by 8 and write down the remainder, a digit from 0 to 7. Repeat with the quotient until it reaches 0, and read the remainders from the bottom up. For 493:
| Step | Remainder |
|---|---|
| 493 ÷ 8 = 61 | 5 |
| 61 ÷ 8 = 7 | 5 |
| 7 ÷ 8 = 0 | 7 |
Read upwards: 493 is 755 in octal, the permission rwxr-xr-x. To check it, 7 × 64 + 5 × 8 + 5 = 493. The step-by-step window above does these divisions for the number you type.
Decimal to octal table
| Decimal | Octal |
|---|---|
| 7 | 7 |
| 8 | 10 |
| 9 | 11 |
| 10 | 12 |
| 16 | 20 |
| 64 | 100 |
| 100 | 144 |
| 255 | 377 |
| 256 | 400 |
| 420 | 644 |
| 493 | 755 |
| 511 | 777 |
| 512 | 1000 |
| 1000 | 1750 |
In octal, 10 is eight, 100 is 64 and 1000 is 512: each place is worth eight times the one to its right. The permission values 644, 755 and 777 are 420, 493 and 511 in decimal.
Have an octal number to read?
The octal to decimal converter multiplies each digit by its power of 8 and adds them up.
For hex and binary at the same time, use the number system converter; for hex alone, the decimal to hex converter.
Decimal to octal questions
10. Eight is one group of eight with nothing left over, the same way ten is 10 in decimal.
144, because 1 × 64 + 4 × 8 + 4 = 100.
Negative numbers, yes: -8 becomes -10, with the sign kept rather than a two's complement form. Fractions such as 2.5 are not converted and show an error.
No practical one. The arithmetic is exact for whole numbers of any length, and the step-by-step window lists up to 40 divisions.
No. The conversion runs in your browser.