Octal Converter
Convert between octal and decimal (and binary/hex) - exact conversion for arbitrarily large numbers.
Enter a number in any base below - this tool converts it to and from octal (base 8) accurately.
Edit either field - the other updates automatically. Supports integers up to JavaScript's safe integer limit (2^53-1).
For dedicated binary/hex converters, see the Binary to Decimal and Hex to Decimal Converters - or the general Number Base Converter for any base.
What Is Octal?
Octal (base 8) uses digits 0-7, where each position represents a power of 8 - historically common in computing (especially Unix file permissions, like chmod 755) because it maps cleanly onto groups of 3 binary bits.
How to Use It
- Enter a number and select its current base (octal, decimal, binary, or hex).
- Select the target base.
- The converted value appears instantly, with invalid digits for the selected base flagged clearly.
Limitations
This handles non-negative integers accurately using BigInt for arbitrarily large values - fractional values aren't supported, since octal fractions require a different interpretation than whole-number octal.