Converter
Binary, Octal, Decimal, Hex & Every Base In Between
Convert any value between base 2 and base 60
Results are provided for informational purposes only and may contain errors. Please verify important information independently. Use of this tool is at your own risk.
How to convert octal to decimal
Convert octal numbers to decimal instantly: type a value and the decimal result appears as you type. Below the converter you'll find the method to do it by hand, a worked example and a table of common values.
- Type or paste a octal number into the box above. Negative numbers and fractions work too.
- The From and To bases are already set to octal and decimal, so the result appears right away: 755 becomes 493.
- Copy the result, or choose any other base from 2 to 60 to convert the same value.
Converting octal to decimal by hand
Number the digits from right to left, starting at 0. Multiply each digit by 8 to the power of its position and add the results together:
755₈ = 7·8² + 5·8¹ + 5·8⁰= 448 + 40 + 5 = 493₁₀
Octal to decimal table
| Octal | Decimal |
|---|---|
0 | 0 |
1 | 1 |
2 | 2 |
7 | 7 |
10 | 8 |
12 | 10 |
17 | 15 |
20 | 16 |
52 | 42 |
100 | 64 |
144 | 100 |
177 | 127 |
377 | 255 |
400 | 256 |
1750 | 1000 |
2000 | 1024 |
Octal and decimal explained
Octal is base 8, with the digits 0 to 7. Each octal digit stands for exactly three bits, which is why Unix file permissions such as 755 are written in octal.
Decimal is base 10, the everyday number system with the digits 0 to 9. Each position is worth ten times the one to its right.
Frequently asked questions
Can I convert negative numbers and fractions?
Yes. Put a minus sign in front of a negative number and use a point for the fraction, for example -12.5. A fraction that never ends in decimal is cut off after 32 digits.
How large can the number be?
There is no practical limit. The converter uses exact whole-number arithmetic, so even numbers with hundreds of digits are converted without rounding.
Do uppercase and lowercase letters matter?
Not up to base 36: FF and ff are the same hexadecimal number. From base 37 upward, uppercase and lowercase letters are different digits.
Is this tool free?
Yes, it's free to use. No signup, no email required. Get results on this page.
How do I get my result?
Use the tool on this page. Your result appears here; no email delivery is required.