How to convert octal to decimal (example: 234)
Multiply each digit by its place value (a power of 8) and add the results:
2×82 + 3×81 + 4×80 = 156
Place value chart
Every digit of 234 (base 8) is worth its value multiplied by a power of 8. Adding the last column gives the decimal value 156.
| Digit | Place value | Contribution |
|---|---|---|
2 | 82 = 64 | 128 |
3 | 81 = 8 | 24 |
4 | 80 = 1 | 4 |
Remember: in base 10 the allowed digits are 0123456789; in base 8 they are 01234567.
Octal to Decimal table
| Octal | Decimal |
|---|---|
0 | 0 |
1 | 1 |
2 | 2 |
3 | 3 |
4 | 4 |
5 | 5 |
7 | 7 |
10 | 8 |
12 | 10 |
17 | 15 |
20 | 16 |
31 | 25 |
40 | 32 |
62 | 50 |
100 | 64 |
144 | 100 |
177 | 127 |
200 | 128 |
377 | 255 |
400 | 256 |
1000 | 512 |
1750 | 1000 |
2000 | 1024 |
3752 | 2026 |
Where number systems are used
- Binary — how CPUs, memory and network packets store every value.
- Octal — Unix/Linux file permissions such as chmod 755.
- Hexadecimal — colour codes (#FF5733), MAC addresses, memory dumps and Unicode code points.
- Decimal — everyday arithmetic, prices and measurements.
About these number systems
Octal
Octal (base 8) uses digits 0–7. It is used for Unix file permissions (e.g. chmod 755).
Decimal
Decimal (base 10) is the everyday number system using digits 0–9.
Frequently asked questions
What is 234 (octal) in decimal?
234 in base 8 equals 156 in base 10.
Can it convert very large numbers?
Yes. The converter uses arbitrary-precision integers (BigInt), so large numbers convert exactly.
Is this useful for HSC ICT?
Yes. Number systems are part of the HSC ICT syllabus in Bangladesh, and the step-by-step method matches textbook solutions.