Octal to Decimal Converter
Convert octal (base-8) numbers to decimal (base-10). Octal numbers use only the digits 0 through 7 — enter any octal value to get its decimal equivalent.
Common Values
How It Works
To convert octal to decimal, multiply each digit by its power of 8 and sum the results. For example, 377: 3×8² + 7×8¹ + 7×8⁰ = 3×64 + 7×8 + 7×1 = 192+56+7 = 255. Working from right to left: position 0 is 8⁰=1, position 1 is 8¹=8, position 2 is 8²=64, and so on.
Worked Examples
| Octal | Decimal |
|---|---|
| 7 | 7 |
| 10 | 8 |
| 17 | 15 |
| 20 | 16 |
| 77 | 63 |
| 100 | 64 |
| 177 | 127 |
| 200 | 128 |
| 377 | 255 |
| 400 | 256 |
Related Conversions
Frequently Asked Questions
- How do I convert octal to decimal?
Multiply each octal digit by 8 raised to its position (starting from 0 on the right). Sum all the results.
- What is octal 777 in decimal?
Octal 777 equals 511 in decimal: 7×64 + 7×8 + 7×1 = 448+56+7 = 511.
- What does chmod 755 mean?
In Unix permissions, 755 is octal. Owner gets 7 (rwx), group gets 5 (r-x), others get 5 (r-x). Each digit is a 3-bit permission mask.
- How do I recognize an octal number?
Octal numbers contain only digits 0-7. In programming code, a leading zero often signals octal (e.g., 0755 in C). This converter accepts any octal digit string.