Octal Converter: The 3-Bit Classic

Created on 9 November, 2025 • Converter Tools • 0 views

Work confidently with octal—convert between octal, decimal, binary, and hex. Understand Unix permission modes, 3-bit groupings, and common pitfalls.

Why Octal Still Matters

Octal (base-8) shines where 3-bit groupings are natural. It’s famous for Unix permission modes (0755, 0644) and appears in embedded/legacy systems. An octal converter helps you move cleanly between octal, decimal, binary, and hex.

Conversions at a Glance

Octal ↔ Decimal

1. Each octal digit represents powers of 8. 0755 (octal) → decimal by 7×8² + 5×8¹ + 5×8⁰.

Octal ↔ Binary

1. Group binary in threes: 111 101 101 → 7 5 5.
2. This makes permission bits easy to read (rwx maps to 111).

Octal ↔ Hex

1. Convert via binary: octal → binary (3-bit groups) → hex (4-bit groups).

Unix Permissions Demystified

Interpreting 0755

1. The leading 0 or 0o marks octal.
2. 7 = rwx (owner), 5 = r-x (group), 5 = r-x (others).
3. Special bits (setuid, setgid, sticky) appear as an extra leading octal digit.

Best Practices and Pitfalls

1. Keep the leading zero when octal is required (0755, not 755).
2. Validate ranges: each octal digit must be 0–7.
3. Don’t mix file permission semantics with ACLs—some systems extend beyond simple octal.