Octal to Decimal Converter
Convert octal (base-8) numbers to decimal (base-10) format instantly. Free online octal to decimal converter with batch conversion support.
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What is Octal to Decimal Conversion?
Octal to decimal conversion transforms numbers from base-8 (octal) to base-10 (decimal) representation. The <a href="https://en.wikipedia.org/wiki/Octal#Usage" target="_blank" rel="noopener">octal system</a> uses digits 0-7, while the decimal system uses digits 0-9. Each octal digit represents three binary bits, making octal a compact way to express binary values.
To convert octal to decimal, multiply each digit by its positional power of 8 and sum the results. For example, octal 377 = 3x8² + 7x8¹ + 7x8⁰ = 192 + 56 + 7 = 255 in decimal. Octal literals are also used in languages like C and Java -- see the <a href="https://www.ibm.com/docs/en/i/7.5?topic=types-octal-integer-constants" target="_blank" rel="noopener">IBM documentation on octal constants</a>.
How to Use This Converter
Enter Octal Values
Type or paste your octal numbers in the input panel. Enter one number per line for batch conversion. The 0o prefix is optional.
Automatic Conversion
The converter automatically transforms each octal number to its decimal equivalent in real time as you type.
Copy or Download Results
Use the Copy button to copy the decimal results to your clipboard, or Download them as a text file.
Conversion Examples
Here are some common octal to decimal conversions:
Octal Input
Decimal Output
Frequently Asked Questions
What digits are valid in the octal system?
The octal number system uses only digits 0 through 7. Any digit 8 or 9 is invalid in octal.
How do I convert octal to decimal manually?
Multiply each digit by 8 raised to the power of its position (starting from 0 on the right), then add the results. For example, 52₈ = 5×8¹ + 2×8⁰ = 40 + 2 = 42₁₀.
Why is octal used in computing?
Octal was historically popular because each octal digit maps to exactly three binary bits, making it a convenient shorthand for binary. It is still used in Unix file permissions (e.g., chmod 755). Many languages support octal literals, including Java and others.
Can I convert multiple octal numbers at once?
Yes! Enter one octal number per line and the converter will process all of them simultaneously. In C++, octal literals are prefixed with 0 -- see the C++ integer literal reference.
Related Tools
Learn more: GeeksforGeeks octal to decimal guide, Math is Fun octal number system, and MDN Web Docs on numbers.