Skip to content
SimpleConvertSimpleConvert

Octal to Decimal Converter

Convert octal numbers (base 8) to decimal (base 10) with power-of-8 expansion.

How to use it

  • Enter octal digits (0-7) to convert to decimal.

Examples

377255

Octal (base 8) uses digits 0-7 only, and is most commonly seen in Unix/Linux file permission modes such as chmod 644 or 755. To read an octal number in decimal, multiply each digit by the power of 8 for its position and sum the results.

Worked example

377: 3 is in the 8² place, 7 in the 8¹ place, 7 in the 8⁰ place. (3×64) + (7×8) + (7×1) = 192 + 56 + 7 = 255.

Where this comes up

  • Understanding what a chmod permission number like 755 actually grants (7 = read+write+execute, 5 = read+execute)
  • Reading legacy system output or older programming language literals that use octal
  • Computer science coursework covering octal alongside binary, decimal and hex
Runs entirely in your browser. Nothing you type is uploaded, logged or shared.

Last updated 18 August 2026