Octal to Decimal
Convert octal to decimal instantly — multiply each octal digit by its power of eight and add the results. Type in either box to convert both ways. Common when reading Unix file permissions, older machine codes and any value written in base eight.
Octal to Decimal conversion table
| Octal | Decimal |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 4 | 4 |
| 10 | 8 |
| 12 | 10 |
| 20 | 16 |
| 40 | 32 |
| 100 | 64 |
| 144 | 100 |
| 200 | 128 |
| 377 | 255 |
| 400 | 256 |
How to convert octal to decimal
To convert octal to decimal, multiply each octal digit by its power of eight and add the results. For example, 12 in octal is 10 in decimal. The converter above validates each digit for its base and updates as you type, and the swap button flips the direction so you can go from decimal back to octal just as quickly.
Frequently asked questions
How do you convert octal to decimal?
To convert octal to decimal, multiply each octal digit by its power of eight and add the results. For example, 12 in octal is 10 in decimal. The converter above does it instantly — type a octal value on the left and the decimal result appears on the right, and you can type in either box to convert in the opposite direction. It only accepts valid digits for each base, so a stray character simply clears the result rather than giving a wrong answer.
What is 12 in decimal?
12 in octal equals 10 in decimal. The conversion table on this page lists common values — 1 is 1, and it continues up to 400 = 256 — so you can read off everyday values at a glance. Any value in between converts exactly too, because the tool carries the full number rather than the rounded figures printed here.
What is the difference between binary, decimal and hexadecimal?
They are just different bases — different numbers of digits before you carry over. Decimal (base 10) is the everyday system with digits 0–9. Binary (base 2) uses only 0 and 1, which is how computers store everything at the hardware level. Hexadecimal (base 16) uses 0–9 then A–F, and is a compact way to write long binary values because each hex digit maps to exactly four bits. The same quantity can be written in any base; only its notation changes.
Is this octal to decimal converter free and accurate?
Yes — it is completely free with no sign-up, and it converts exactly using the standard positional method, validating that every digit is legal for its base. Common when reading Unix file permissions, older machine codes and any value written in base eight. Everything runs locally in your browser, so nothing you enter is uploaded or stored. For octal, custom bases and step-by-step breakdowns, the full number base converter handles any base from 2 to 36.
More conversions
Decimal → OctalOctal → BinaryBinary → OctalHexadecimal → OctalOctal → HexadecimalBinary → DecimalDecimal → BinaryHexadecimal → DecimalDecimal → HexadecimalBinary → HexadecimalHexadecimal → Binary Number base converter →