Hex to Octal

Hex to Octal Converter

Convert hexadecimal (base 16) numbers to octal (base 8) without doing the math through decimal yourself. Paste one number per line and read the results immediately: FF → 377, 1ED → 755, 0x1000 → 10000. The reverse mode converts octal back to hex.

How hex to octal conversion works

Hex and octal are both powers of two, so the easiest path is through binary:

1. Write each hex digit as four bits: 1ED → 0001 1110 1101.
2. Regroup the bits into threes from the right: 000 111 101 101.
3. Replace each group with an octal digit: 0 7 5 5 → 755.

Going through decimal works as well (0x1ED = 493 = 7 × 64 + 5 × 8 + 5), but the binary method avoids long division. The converter uses exact big-integer arithmetic, so it gives the right answer for numbers of any length.

Why convert between hex and octal?

Hex dominates modern computing, but octal survives in a few important places: Unix file modes and umask values, stat output, tar and cpio archive headers, and octal escape sequences in C strings such as \033 for the escape character (0x1B). When a tool prints a mode in hex (for example 0x81ED from a raw inode) and you need the familiar 100755, this converter does it in one step.

Options

• Prefix – output 0o (octal) or 0x (hex) literals.
• Uppercase – choose 1ED or 1ed for hex output.
• Group digits – three-digit groups for octal, four-digit groups for hex.

Fractions (0.8 hex = 0.4 octal) and negative numbers are handled. For a full view across all bases, open the All Number Converter.