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Octal to Decimal Converter

Enter an octal number to instantly get its decimal, binary, and hexadecimal equivalents.

Last updated: May 30, 2026

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

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What is Octal to Decimal Converter?

Octal (base 8) uses digits 0–7. To convert an octal number to decimal, multiply each digit by 8 raised to its positional power (starting from the right at 0) and sum the results.

For example, octal 377: - 3 × 8² = 3 × 64 = 192 - 7 × 8¹ = 7 × 8 = 56 - 7 × 8⁰ = 7 × 1 = 7 Total: 192 + 56 + 7 = 255

Octal 755 (a familiar Unix permission): - 7 × 64 = 448, 5 × 8 = 40, 5 × 1 = 5 → decimal 493

How to Use Octal to Decimal Converter

1

Type or paste an octal number in the input field (only digits 0–7).

2

The decimal, binary, and hex outputs update in real time.

3

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

4

Click "Load Sample" to see an example.

Common Use Cases

  • Translating Unix chmod permission values to human-readable decimal.
  • Learning the octal number system in computer science courses.
  • Decoding octal-encoded values in legacy configuration files.

Example Input and Output

Octal 377 converts to decimal 255 — the maximum value for an 8-bit byte.

Octal
377
Decimal
255

Data Privacy

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

Frequently Asked Questions

Can I enter a leading zero?
Yes. In C/Unix convention, a leading zero indicates octal notation (e.g. 0755). This tool strips it automatically.
What is the decimal value of octal 644?
6 × 64 + 4 × 8 + 4 = 384 + 32 + 4 = 420. Octal 644 is decimal 420, the permission for owner read/write, group/others read-only.
Does this handle large octal numbers?
Yes. BigInt is used internally so there is no practical limit on input size.

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