Hex to Octal Converter

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Convert a hexadecimal number to octal. Hex and octal do not share an integer ratio of bits per digit (4 vs 3), so the converter parses the hex string into a canonical integer and re-formats it in base 8: ff becomes 377, 1ed becomes 755. Useful when exchanging values between hex-first tools (debuggers, hashes, color codes) and octal-first tools (chmod, umask, vintage Unix utilities). Long values are handled exactly with BigInt.

Hexadecimal (16)

Allowed: 0–9, a–f

Octal (8)

Allowed: 0–7

Hexadecimal (16) → Octal (8)

Quick reference table

Hexadecimal (16)Octal (8)
a12
1020
2040
40100
64144
ff377
fff7777

Glossary

Hexadecimal (base 16)

The hexadecimal numeral system uses sixteen digits: 0–9 and a–f, where a–f represent 10–15. Each hex digit maps to exactly four binary digits (one nibble), which makes hex the compact human-readable form of binary data. Memory addresses, MAC addresses, MD5/SHA hashes, RGB color codes such as #ff8800 and machine-code bytes are all conventionally written in hex.

Octal (base 8)

The octal numeral system uses digits 0 through 7. It was popular in early computing because each octal digit maps cleanly to exactly three binary digits, which made it convenient for systems with 12-, 24- or 36-bit words. Today its most common surviving use is Unix file permissions: chmod 755 means owner-rwx, group-rx, others-rx, where each digit is a 3-bit permission mask.

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