Convert Octal to Hex

JavaScript’s regular Number type loses integer precision above 2^53 (about 16-17 decimal digits, or 18 octal digits). For values larger than that, parseInt‘s result rounds to the nearest representable float. This tool uses BigInt('0o' + clean).toString(16) which handles any size exactly. So a 60-octal-digit input gets its full 80-hex-digit result, not silently truncated.

No semantic difference – hex is case-insensitive. Common conventions: UPPERCASE in datasheets, hardware register dumps, assembler addresses, color codes (#FF0000); lowercase in C/C++ source (0xff), most modern style guides, and CSS. Pick whichever your destination expects. Toggle the checkbox to see the result update live.

It’s a marker signaling “the following digits are hexadecimal, not decimal” – required syntax in C/C++/Java/JS source code (int x = 0xFF;). Some assemblers use $ instead ($FF), or a trailing h (FFh). Some shell contexts don’t want any prefix at all (raw hex pipe). Toggle the checkbox to match your destination.

Mathematically it doesn’t have to – you could group octal digits in pairs of three bits and regroup into nibbles of four. But the BigInt implementation goes via the canonical numeric value: parse the octal string as a BigInt, then format that BigInt as hex. Same result, simpler code, exact precision.

3-digit octals like 755 and 4-digit like 04755 are commonly file permission modes from chmod. The decoder shows the ls -l-style rwxr-xr-x form. Each octal digit = a read/write/execute triplet: 7 = rwx, 6 = rw-, 5 = r-x, etc. The leading digit of a 4-digit mode controls setuid/setgid/sticky bits.

Unlimited (BigInt). A 100-digit octal becomes a ~83-digit hex value, computed exactly. Practical use is usually under 30 digits.

Both are power-of-2 bases (8 = 2³, 16 = 2⁴), so both map cleanly to binary. Octal groups bits in triples; hex in nibbles. The choice between them is historical: octal was popular when computers used 12/24/36-bit words (which factor evenly into 3s). Hex won out with 8/16/32/64-bit byte-aligned systems because hex groups byte-aligned (2 hex digits = 1 byte).

No – the permission decode operates on the original octal string, not the padded hex/binary. 0755 with bit width 32 still decodes as rwxr-xr-x, even though the displayed binary is 00000000000000000000000111101101 (padded).

No. All BigInt parsing, formatting, and permission decoding run in your browser. Open DevTools → Network and confirm zero requests fire after the page loads – even when you Convert.

Yes. Total bundle is under 22 KB. Once loaded, disconnect and keep converting. Useful for embedded-system permission audits or assembler work without internet.