Octal to Decimal Converter

How octal works

Octal is base 8, using only digits 0-7. Each position represents a power of 8, just as decimal positions represent powers of 10. The tool validates that your input contains only 0-7, then hands it to JavaScript's parseInt(value, 8) to do the base conversion.

Worked example

The placeholder value 755 — a permission mode familiar from Unix chmod — converts as: 7×8² + 5×8¹ + 5×8⁰ = 7×64 + 5×8 + 5×1 = 448 + 40 + 5 = 493.

More conversions

Where octal still shows up

Octal was common in early computing (word sizes divisible by 3 bits) and survives today mainly in Unix/Linux file permissions (chmod 755, umask 022) and some legacy escape-sequence notations — outside those contexts, hexadecimal has largely replaced it for representing binary data.