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Binary to Octal Converter

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Convert a binary number to octal. Each group of three binary digits maps cleanly to one octal digit, so 111101101 becomes 755 — the binary form of the chmod 755 permission mask. Useful when reading raw permission bits returned by stat() or when working on systems where octal is the conventional shorthand for grouped binary flags. Negative values keep a leading minus sign in both bases.

From (Binary (2))

Binary (2)

Allowed: 0 and 1

To (Octal (8))

Octal (8)

Allowed: 0–7

Binary (2) → Octal (8)

Quick reference table

Binary (2)	Octal (8)
111	7
1000	10
1000000	100
111111111	777
1000000000	1000
111111111111	7777

Glossary

Binary (base 2)

The binary numeral system uses only two digits — 0 and 1 — and is the native number system of every digital computer. Each binary digit (bit) represents a power of 2: the rightmost bit is 2^0 = 1, then 2^1 = 2, 2^2 = 4, 2^3 = 8 and so on. Eight bits form one byte. Binary underlies every memory cell, register and network packet.

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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