Octal Converter

Convert numbers to and from octal (base 8). Entering a three-digit octal number also shows it as Unix file permissions.

How to use the Octal Converter

Enter a number.
Choose the base it is in.
Read the octal, decimal, binary and hex values.

How it works

Octal uses digits 0–7, and each position is a power of 8. 755 in octal = 7 × 64 + 5 × 8 + 5 = 493 in decimal. Each octal digit maps to exactly three binary digits, which is why Unix permissions use octal: 7 = rwx (read, write, execute), 5 = r-x, 4 = r--.

Common Unix permissions

Octal	Permissions	Meaning
755	rwxr-xr-x	Owner full; others read & execute
644	rw-r--r--	Owner read/write; others read
700	rwx------	Owner only
600	rw-------	Private file
777	rwxrwxrwx	Everyone full access (avoid)

Frequently asked questions

What is 755 in decimal?

493.

What does chmod 644 mean?

Owner can read and write; group and others can only read.

What is 10 in octal?

8 in decimal.

Why is octal used?

Each digit represents three bits, a compact way to write binary groups such as file permissions.

How do I convert decimal to octal?

Divide by 8 repeatedly and read the remainders from bottom to top: 493 → 61 r5 → 7 r5 → 0 r7 → 755.