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Decimal to Octal Converter

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Convert a decimal integer to octal. The number is divided by 8 repeatedly and the remainders, read bottom-up, form the octal digits — so 493 in decimal becomes 755 in octal, the familiar chmod value for an executable. Useful for translating numeric permission masks back into the form that chmod and umask understand, and for grouping binary values in 3-bit chunks the way mainframes once did.

From (Decimal (10))

Decimal (10)

Allowed: 0–9

To (Octal (8))

Octal (8)

Allowed: 0–7

Decimal (10) → Octal (8)

Quick reference table

Decimal (10)	Octal (8)
7	7
8	10
10	12
64	100
100	144
420	644
493	755
511	777
1024	2000
4095	7777

Glossary

Decimal (base 10)

The decimal numeral system is the everyday number system used by humans, with digits 0 through 9. Each digit position represents a power of 10 — units, tens, hundreds, thousands. It is sometimes called base-10 or denary. All four bases on this page convert through decimal as a canonical integer value, so a round-trip such as binary → decimal → hex always produces the exact same number.

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.

Related tools

Octal to Decimal

Convert octal numbers (base 8) to decimal — handy for Unix permissions

Decimal to Binary

Convert decimal integers to binary (base 2) — with BigInt support

Decimal to Hex

Convert decimal integers to hexadecimal — with optional uppercase output

Number Base Converter

Convert integers between binary, octal, decimal and hexadecimal — with full BigInt support