Octal to Binary Converter
Enter an octal number to instantly see its binary, decimal, and hexadecimal equivalents.
Last updated: May 30, 2026
Find this tool useful? Support the project to keep it free!
Buy me a coffeeWhat is Octal to Binary Converter?
Octal (base 8) uses digits 0–7, with each octal digit representing exactly 3 binary bits. This tight relationship makes octal-to-binary conversion straightforward: replace each octal digit with its corresponding 3-bit binary group.
Octal digit → 3-bit binary: - 0 → 000, 1 → 001, 2 → 010, 3 → 011 - 4 → 100, 5 → 101, 6 → 110, 7 → 111
For example, octal 377: - 3 → 011, 7 → 111, 7 → 111 - Binary: 011111111 = 11111111 (leading zeros stripped) = 255 decimal
How to Use Octal to Binary Converter
Type or paste an octal number in the input field (digits 0–7 only).
The binary, decimal, and hex outputs are updated instantly.
Click any copy button to copy the result to your clipboard.
Click "Load Sample" to see an example.
Common Use Cases
- Understanding Unix chmod permission bits (e.g. 755 → binary 111 101 101).
- Converting octal values in embedded systems or legacy code to binary for bit inspection.
- Computer science coursework on number base systems.
Example Input and Output
Octal 755 (the common Unix read/write/execute permission) converts to binary 111101101.
755111101101Data Privacy
All conversions run entirely in your browser. No data is sent to any server.
Frequently Asked Questions
Why does each octal digit map to 3 binary bits?
Because 8 = 2³. Each octal digit (0–7) can be expressed as exactly 3 binary digits (000–111), making the mapping clean and lossless.
What octal digits are valid?
Only digits 0 through 7. The digits 8 and 9 do not exist in base-8 notation.
Does this support large octal values?
Yes. BigInt is used internally, so there is no practical size limit.
Related Tools
Binary to Octal Converter
Convert binary numbers (base 2) to octal (base 8). Also shows decimal and hexadecimal equivalents. Supports large binary numbers with BigInt precision.
Octal to Decimal Converter
Convert octal (base 8) numbers to decimal (base 10), binary, and hexadecimal. Supports arbitrarily large values via BigInt.
Octal to Hex Converter
Convert octal (base 8) numbers to hexadecimal (base 16), decimal, and binary. Uses BigInt for precision on large values.
Decimal to Octal Converter
Convert decimal integers to octal (base 8) notation. Also shows binary and hexadecimal outputs. Supports arbitrarily large numbers.
Hex to Octal Converter
Convert hexadecimal numbers to octal (base 8), decimal, and binary. Accepts 0x prefix. Uses BigInt for arbitrarily large values.
Hex to Binary Converter
Convert hexadecimal numbers to binary (base 2), decimal, and octal. Supports 0x prefix and arbitrarily large hex values.