Decimal to Octal Converter

Octal is base 8, using only digits 0-7. It's best known for Unix and Linux file permissions — commands like chmod 755 use octal because each digit maps cleanly to 3 binary bits (read/write/execute flags). To convert decimal to octal, divide repeatedly by 8 and read the remainders bottom to top.

Worked example

64 ÷ 8 = 8 remainder 0. 8 ÷ 8 = 1 remainder 0. 1 ÷ 8 = 0 remainder 1. Reading bottom to top: 100. So decimal 64 is octal 100 (64 = 8², one full 'octal hundred').

255 ÷ 8 = 31 remainder 7. 31 ÷ 8 = 3 remainder 7. 3 ÷ 8 = 0 remainder 3. Reading bottom to top: 377.

Where this comes up

• Setting Unix/Linux file permissions with chmod, which take octal values like 644 or 755
• Legacy systems and older programming languages that used octal for byte representation
• Computer science coursework covering the full family of number bases