Octal to Decimal Converter
Convert octal (base-8) numbers to decimal (base-10).
Try an example:
- Binary (2)
11111111- Octal (8)
377- Decimal (10)
255- Hexadecimal (16)
ff
Converting Octal to Decimal
Converting octal to decimal turns base-8 values — common in file permissions — back into ordinary numbers.
How to convert Octal to Decimal by hand
- Write the place values (1, 8, 64, …) under each digit, from the right.
- Multiply each digit by its place value.
- Add the results together.
Worked example
100 (octal) → 64 (decimal) — 1×64 + 0×8 + 0×1 = 64.
More converters
- Decimal to Binary
- Binary to Decimal
- Decimal to Hexadecimal
- Hexadecimal to Decimal
- Binary to Hexadecimal
- Hexadecimal to Binary
Frequently asked questions
How do I convert Octal to Decimal?
Write the place values (1, 8, 64, …) under each digit, from the right. Multiply each digit by its place value. Add the results together. Or just use the converter on this page — it does it instantly. Example: 100 (octal) becomes 64 (decimal).
What is 100 (octal) in decimal?
100 (octal) converts to 64 (decimal). 1×64 + 0×8 + 0×1 = 64.
Is this converter free and private?
Yes — it is free and unlimited, and the conversion runs entirely in your browser, so nothing is uploaded to a server.