Encoding desk
Octal to Decimal
Convert a signed octal integer to decimal using exact arithmetic.
Octal to Decimal: Interpret digits in base eight and return their decimal value. Octal to Decimal is useful for checking an octal worksheet or the numeric magnitude of a permission-like code. The page converts the whole integer; it does not decide what those digits grant in an operating system. Runs 100% locally in your browser with zero server file uploads.
- Category
- Developer tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Result
ReadyConversions run locally. Numeric values are integers, signs are normalized, and prefixes such as 0b or 0o are intentionally not accepted.
Powers of eight and an example
For octal digit d_i at position i counted from zero on the right, magnitude N = sum of d_i × 8^i. Input 157 gives 1×64 + 5×8 + 7×1 = 64 + 40 + 7 = 111, and the output is 111. Each octal digit corresponds to three ordinary binary bits: 1, 5 and 7 expand to 001, 101 and 111. That grouping is a base conversion, not BCD, which groups decimal digits separately.
Reading a numeral rather than a machine field
The Sonoma State account of number codes (https://bob.cs.sonoma.edu/IntroCompOrg-RPi/sec-codes.html) distinguishes digit encodings such as BCD from ordinary positional numbers. Here the octal digits describe one exact magnitude, with no byte-order reversal or implicit two’s-complement width. Up to 256 input characters and 1,024 output characters are allowed. Leading plus and minus signs are accepted, but spaces, fractional parts and 0o are not. Values beyond 9,007,199,254,740,991 remain exact in this conversion; JavaScript Number has a different precision boundary (https://tc39.es/ecma262/multipage/numbers-and-dates.html#sec-number.max_safe_integer), which matters if another program parses the exported decimal. The chmod calculator interprets permission digits when that context is needed.
How to use it
- Enter the value in the format shown below.
- Run the conversion and check the result against your source convention.
- Copy or download the output in the form required by your destination.
Privacy & limitations
Conversion runs in your browser. Your values and results are not uploaded.
Related tools
Frequently asked questions
Why are 8 and 9 invalid in an octal entry?
Base eight has only digits 0 through 7. A digit 8 would require a carry to the next place, just as a single decimal digit cannot represent ten. If your source includes 8 or 9, check whether it is actually decimal rather than deleting those digits.
Does a leading zero change how the tool reads my value?
Every entry is already interpreted as octal, so 010 and 10 both return decimal 8. The literal prefix 0o is rejected here. Do not transfer that assumption to other applications: their configuration parser decides whether a leading zero is meaningful or whether the value is decimal.
Does converting 755 tell me whether a file is secure?
No. It gives the numeric value 493 and does not inspect a file, ownership or access rules. The same digits may describe permissions in a particular context, but the conversion alone cannot assess that context. A minus sign is a mathematical sign, not a permission flag.
Free tool · runs in your browser · no account required