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Octal to Decimal Converter

Convert octal numbers to decimal, binary and hexadecimal.

To convert octal to decimal, enter a base-8 value above using digits 0 to 7. Octal is still used for Unix file permissions, where each digit encodes read, write and execute bits for one class of user.

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Frequently asked questions

Where is octal still used?

Unix file permissions, almost exclusively. chmod 755 is octal because each digit encodes exactly three permission bits — read, write and execute — which is the one place base 8 aligns neatly with the underlying data.

Why does a leading zero change a number in some languages?

Because C and its descendants historically treated a leading zero as an octal prefix, so 010 meant 8. It is a notorious source of bugs in date handling, and modern languages either removed it or require an explicit 0o prefix.

How to use the octal to decimal converter

  1. 1Enter or paste your value.
  2. 2The result appears immediately — copy or download it.

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