About the Hex to Octal Converter
Hexadecimal and octal are both short ways to write binary. A hex digit stands for four bits and an octal digit for three, so converting between them is not as direct as it looks. This tool does it exactly: paste hex numbers one per line, with or without the 0x prefix, and read the octal values on the right. You can add the 0o prefix to the output. Large values are handled without rounding and negative numbers keep their sign. Lines that are not valid hex are flagged and left alone. The conversion runs in your browser and nothing is uploaded.
Updated October 2026
How to use the Hex to Octal Converter
- 1Type or paste hexadecimal numbers, one per line.
- 2A 0x prefix and capital or small letters are accepted.
- 3Tick Add the 0o prefix if you want it on the results.
- 4Read the octal numbers on the right.
- 5Copy the result or download it.
When you need this
Octal is the notation of Unix permissions and some older systems, while hex is the norm elsewhere in computing. When a value is given in hex, for instance a mode from a system call or a header, translating it to octal makes it readable as permissions. Embedded and legacy documentation sometimes switches between the two as well.
A list converter is useful when a table of values is in one base and your tool wants the other.
Worked examples
Hex FF becomes octal 377. Hex 1FF becomes 777, which is the permission set rwxrwxrwx. Hex CAFE becomes 145376. Each step is exact, so you can use the result in code without checking for rounding.
- FF → 377
- 1FF → 777
- 1A4 → 644
- CAFE → 145376
Related tools
For decimal results use the Hex to Decimal Converter, and for the opposite direction, from octal, use the Octal to Decimal Converter. The Number Base Converter shows binary, octal, decimal and hex side by side.
Using it on phone and computer
Paste hexadecimal numbers, one per line, into the left box and the result appears straight away, so there is no button to press. On a phone, long-press the box to paste and use the Copy button to move the result to another app. On a computer you can also download it as a text file. It saves a round trip through a calculator when a table of values is in hex and your target system wants octal.
Accuracy and limits
As a check, 8 in hex is 10 in octal and 40 in hex is 100 in octal. The tool works with exact whole-number arithmetic rather than floating point, so long values are not rounded. Anything it cannot read is shown with a warning that names the line, and the rest of your list is still converted. Nothing you paste is uploaded or stored, and closing the tab removes it.
Features
- Many numbers at once
- Accepts 0x prefix
- Optional 0o prefix on the output
- Exact for very large numbers
- Negative numbers supported
- Bad lines flagged, not dropped
Frequently asked questions
How do I convert hex to octal?
The simplest way is through binary or decimal. Write each hex digit as four bits, regroup the bits in threes from the right, and write each group as an octal digit. The tool does this at once for a list.
What is FF in octal?
377. FF is 255 in decimal, and 255 is 3 times 64 plus 7 times 8 plus 7, written 377.
What is 1A4 in octal?
644. Hex 1A4 is 420 in decimal, which is the common Unix permission 644 for an ordinary file: read and write for the owner, read for others.
Why can't I just regroup the digits?
Hex digits are four bits and octal digits are three bits, so the groups do not line up. A hex digit can spread across two octal digits. That is why a converter or an intermediate binary step is needed.
Does the tool accept the 0x prefix?
Yes. 0x1A4, 1A4 and 1a4 give the same result. A trailing h, as used in assembly language, is accepted as well.
Is my data uploaded?
No. The conversion happens in your browser and your numbers stay on your device.