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Enter hex values and get their octal equivalents instantly. The conversion goes through binary as an intermediate - the tool handles all steps automatically.
Hexadecimal value (0-9, A-F)
Octal (base-8)
Hex and octal do not share a direct base relationship the way hex and binary do (hex uses groups of 4 bits, octal uses groups of 3 bits, and 4 and 3 do not divide evenly into each other). As a result, converting between them requires going through decimal or binary as an intermediate step. Going through binary is the more mechanical approach and is less error-prone by hand.
Embedded systems work is one context where you might need this conversion. Many real-time operating systems and hardware abstraction layers accept register configuration values in octal notation, while datasheets and reference manuals express addresses and values in hex. Being able to move between the two bases without introducing arithmetic errors is useful.
Some Unix utilities, particularly older ones, accept numeric arguments in octal by default or output values in octal. If you have a hex value from a modern tool and need to pass it to one of those utilities, converting it to octal is necessary.
The cleanest way to convert hex to octal by hand is to expand each hex digit to 4 binary bits, then regroup those bits into groups of 3 from the right (padding the leftmost group if needed), and finally replace each 3-bit group with its octal digit.
For example, 0xFF in hex expands to 11111111 in binary. Regrouping into threes from the right: 11 and 111 and 111. Padding the first group: 011 111 111. Each group is 3, 7, 7, giving the octal value 377. You can verify this: (3 x 64) + (7 x 8) + (7 x 1) = 192 + 56 + 7 = 255, which is 0xFF in decimal.
The tool performs all three steps - hex to binary, regrouping, binary to octal - internally. You only need to supply the hex input and read the octal output.
In C, C++, and many languages derived from them, an integer literal with a leading zero is interpreted as octal. Writing 0755 in a C program is not the decimal number seven hundred fifty-five; it is the octal number 755, which equals 493 in decimal. This is the same notation used in chmod calls in C system programs.
If you are reading code that uses hex constants and need to produce the equivalent octal literal for use in a different context, paste the hex values here and get the octal forms to use with the leading-zero prefix in your source.
Can I enter multiple hex values at once?
Yes. Put each hex value on a separate line or separate them with spaces. The converter processes all of them and displays the corresponding octal values in the same order.
What is 0xFF in octal?
0xFF equals 255 in decimal and 377 in octal. The binary intermediate is 11111111, which regroups as 011 111 111 (3, 7, 7).
Does the output include a leading zero for C-style octal literals?
No. The converter outputs minimal octal digits without any prefix. Add the leading 0 manually if you need it for a C or C++ literal.