Convert octal to decimal as you type, with every step shown. This free online converter gives exact results for numbers of any size, and nothing you type leaves your browser.
1 Enter your value
From
To
0x
Examples
2 Your answer
Decimal
dec
Show in other bases
Tap any value to copy it.
See the working
Guide
How it works
Three steps, whether you are reading a memory address, a bit flag or a byte value.
1
Choose what to convert
Pick what you have and what you want: decimal, hexadecimal, binary or octal.
2
Type or paste a value
Write it however you like: 65,535, 0xFF, FFh, with commas, spaces or underscores.
3
Read the answer
It appears as you type, in every other base, with the working shown.
The formulas
A digit's value depends on its position. Every answer here uses one of these rules:
Octal to decimal
decimal = Σ digit × 8position
0o643 is 6 × 64 + 4 × 8 + 3 × 1 = 419, so the answer checks out.
Decimal to octal
divide by 8, keep the remainders
419 ÷ 8 = 52 r 3, 52 ÷ 8 = 6 r 4, 6 ÷ 8 = 0 r 6, so 419 is 0o643.
Octal to binary
each octal digit = 3 binary bits
0o643 is 6 → 110, 4 → 100, 3 → 011, so 0o643 is 110 100 011.
Decimal to hexadecimal digit chart
The decimal values 0 to 15 are the single hexadecimal digits 0 to F. Click one to add it to the converter.
All conversions
Decimal, hexadecimal, binary and octal converter
One free tool for every direction. Use it as a decimal to hexadecimal converter, convert decimal to binary or octal, or work backwards as a hexadecimal to decimal converter that turns 0x to decimal values. It also converts hexadecimal to binary, binary to hexadecimal and octal to decimal, so it works as a full number base converter and hexadecimal calculator. Pick a conversion to start.
Use this octal to decimal table as a quick octal to decimal chart for common values, from 0 to 65,535.
Octal
Decimal
0
0
1
1
2
2
3
3
4
4
5
5
6
6
7
7
10
8
11
9
12
10
13
11
14
12
15
13
16
14
17
15
20
16
40
32
100
64
144
100
177
127
200
128
377
255
400
256
1000
512
1750
1,000
2000
1,024
10000
4,096
177777
65,535
Help
Questions
Quick answers to what people most often ask about hexadecimal, decimal and binary.
01How do I convert octal to decimal?
To convert octal to decimal, number the digits from the right, starting at 0. Multiply each digit by 8 raised to the power of its position. Add the results together to get the decimal number.
02What is 377 in decimal?
0o377 in octal is 255 in decimal. Type 377 into the converter above to see every step.
03What is 2000 in decimal?
0o2000 in octal is 1,024 in decimal.
04What is 10 in decimal?
0o10 in octal is 8 in decimal.
05What is 755 in decimal?
0o755 in octal is 493 in decimal. It is the 755 in chmod 755 (rwxr-xr-x).
06What is 777 in decimal?
0o777 in octal is 511 in decimal. It is the 777 in chmod 777: read, write and execute for everyone.
07Where is octal still used?
Mostly in Unix and Linux file permissions, such as chmod 755, where each octal digit sets the read, write and execute bits for one group of users. It also appears in some older systems and programming languages, often written with a 0o prefix.
08How do I convert octal to decimal in Excel?
Use the OCT2DEC function: =OCT2DEC("377") returns 255. It works the same way in Google Sheets. These functions only handle up to 10 input characters, and the binary ones only −512 to 511, so use this converter for larger numbers.
09How do I convert octal to decimal in Python or JavaScript?
In Python, int('377', 8) returns 255. In JavaScript, parseInt('377', 8) returns 255. Python handles any size; in JavaScript use BigInt for numbers above 2⁵³.
10Does the converter use two’s complement for negative numbers?
No. It keeps the minus sign, so −255 is −0xFF, −0b11111111 and −0o377. Computers usually store negative numbers in two’s complement, where the pattern depends on the width: −1 is 1111 1111 (0xFF) in 8 bits and 0xFFFF in 16 bits. To read a signed value whose top bit is set, subtract 2ⁿ: 0xFF as a signed 8-bit number is 255 − 256 = −1.
11Can I convert octal numbers with a fractional part?
The converter works with whole numbers. By hand, convert the fractional part by multiplying it by the target base again and again and keeping the whole-number part each time. For example, 0.5 × 16 = 8, so 0.5 is 0x0.8 in hexadecimal, 0b0.1 in binary and 0o0.4 in octal.
12Is there a limit to how big a octal number can be?
No. The converter uses exact whole-number arithmetic, so 64-bit, 128-bit and longer octal values convert to decimal with every digit correct, with no rounding.
13What does “oct to dec” mean?
“oct to dec” is short for octal to decimal, which means going from base 8 to base 10: a number written in base 8 is rewritten in base 10. For example, 0o377 becomes 255.
14Does this octal to decimal calculator show the working?
Yes. It converts octal to decimal with steps: open “See the working” under the answer to see each digit multiplied by its power of 8. Every answer is also shown in decimal, hexadecimal, binary and octal at once.
15Is this octal to decimal converter free?
Yes. It is free with no sign-up, works online on phones, tablets and computers, and every octal to decimal conversion runs in your browser, so nothing you type is sent anywhere.