Octal to Decimal Converter

Convert base-8 octal numbers to base-10 decimal values instantly. This tool validates octal digits, supports large integers with JavaScript BigInt, and updates results in real time as you type. For the reverse conversion, try our Decimal to Octal Converter.

How octal to decimal conversion works

Each octal digit represents a power of eight. The rightmost digit is $8^0$, the next is $8^1$, and so on. For example, octal $377$ equals $3 \times 8^2 + 7 \times 8^1 + 7 \times 8^0 = 255$ in decimal.

Common use cases

Unix file permission values such as 755 and 644.
Legacy computing and embedded systems documentation.
Learning number base conversions alongside Octal to Hex Converter.

Frequently Asked Questions

Which digits are valid in octal?

Only digits 0 through 7 are valid in octal notation.

Can this convert negative octal numbers?

This version accepts unsigned octal integers. Negative values are not supported.

Is there a size limit?

The tool uses BigInt, so it can handle very long octal strings within normal browser limits.

Are my numbers uploaded to a server?

No. Conversion runs entirely in your browser.

Report

Octal to Decimal Converter