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Decimal to Octal Converter

Enter a decimal integer to instantly convert it to octal (base 8), along with binary and hexadecimal outputs.

Last updated: May 30, 2026

Client-Side Processing
Input Data Stays on Device
Instant Local Execution

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What is Decimal to Octal Converter?

The decimal (base 10) number system uses digits 0–9 and is the standard system used in everyday arithmetic. Octal (base 8) uses digits 0–7 and was historically important in early computing where byte sizes were multiples of 3 bits. Today octal is most commonly encountered in Unix file permissions (e.g. chmod 755).

To convert decimal to octal, repeatedly divide the number by 8 and collect the remainders from bottom to top. For example, converting 255: - 255 ÷ 8 = 31 remainder 7 - 31 ÷ 8 = 3 remainder 7 - 3 ÷ 8 = 0 remainder 3 Reading remainders upward: 377 — so 255 decimal = 377 octal.

How to Use Decimal to Octal Converter

1

Type or paste a decimal integer in the input field.

2

The octal, binary, and hexadecimal outputs update instantly.

3

Click any copy button to copy the result to your clipboard.

4

Click "Load Sample" to see an example conversion.

Common Use Cases

  • Converting Unix file permission values (like 755 or 644) from decimal to octal.
  • Learning about different number bases in computer science coursework.
  • Networking exercises involving IP address octal encoding.
  • Preparing for certification exams (CCNA, CompTIA) covering number systems.

Example Input and Output

The decimal number 255 converts to octal 377 — the well-known Unix permission 0377.

Decimal Integer
255
Octal
377

Data Privacy

All conversions run entirely in your browser. No data is sent to any external server.

Frequently Asked Questions

What digits are used in octal?
Octal uses only the digits 0, 1, 2, 3, 4, 5, 6, and 7. The digit 8 and 9 do not exist in base-8 notation.
How is octal used in Unix permissions?
Unix file permissions are represented as three groups of three bits (rwx for owner, group, others). Each group of three bits has a maximum value of 7, making octal a natural fit. chmod 755 means 7 (rwx) for owner, 5 (r-x) for group and others.
Does this handle very large numbers?
Yes. The converter uses JavaScript's BigInt, which supports arbitrarily large integers without precision loss.

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