Octal to decimal converter

Convert an octal (base 8) number to decimal. Shows place value expansion.

Octal

Octal system

Base 8 uses digits 0–7. Each position is a power of 8. 77₈ = 7×8 + 7 = 63. 100₈ = 64.

Uses

Unix file permissions (chmod 755 = rwxr-xr-x). Early computing. Each octal digit = exactly 3 binary digits.

Examples
77₈ = 63 755₈ (chmod) 100₈ = 64 777₈ = 511
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