Octal to Decimal

What is the Octal to Decimal Converter?

This tool converts octal numbers (base-8) to decimal numbers (base-10), useful for system administration and legacy computing.

Why Convert Octal to Decimal?

Octal conversion is important for:

• Unix/Linux permissions — chmod 755 means different access levels
• Legacy systems — older computers used octal notation
• Programming — some languages support octal literals (0o755)
• Digital systems — grouping binary into 3-bit chunks

The Conversion

Each octal digit represents a power of 8, from right to left.

Example: 755 = 7×64 + 5×8 + 5×1 = 448 + 40 + 5 = 493

How to Use

1. Enter octal number — use digits 0-7 only
2. View decimal result — conversion is automatic
3. Understand the value — useful for permission calculations

Unix Permission Examples

• 644 = 420 (rw-r--r--)
• 755 = 493 (rwxr-xr-x)
• 777 = 511 (rwxrwxrwx)
• 400 = 256 (r--------)

Note

Digits 8 and 9 are not valid in octal and will be rejected.