Number Base Converter
Convert between decimal, hexadecimal, binary and octal — free, live, four-way, with arbitrary-precision BigInt so large numbers stay exact.
100% private — runs entirely in your browser. Nothing you enter is uploaded or logged.
Uses arbitrary-precision BigInt, so very large integers convert exactly (native JavaScript numbers lose precision above 2⁵³). Prefixes like 0x and 0b are accepted. Calculated locally.
How to use the Number Base Converter
- Type a value in decimal, hex, octal or binary.
- The other three bases update instantly.
- Toggle digit grouping for readability.
- Prefixes like 0x and 0b are accepted.
What you can use it for
- Convert hex colour or byte values to decimal
- Work with binary and hex in low-level code
- Convert large integers exactly with BigInt
- Check the 0x/0b representation of a number
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Browse all free developer tools →Frequently asked questions
How do I convert hex to decimal?
Type the hex value (with or without a 0x prefix) and the decimal, binary and octal fields update instantly.
What is 0xFF in decimal?
255 — and 11111111 in binary, 377 in octal. Enter it and all bases fill in.
How do I convert binary to hex?
Enter the binary digits in the binary field; the hexadecimal equivalent appears in the hex field automatically.
Does it handle very large numbers?
Yes — it uses BigInt, so integers far beyond JavaScript's normal 2^53 limit convert exactly with no rounding.
What do the 0x and 0b prefixes mean?
0x marks a hexadecimal number and 0b marks a binary one; the converter accepts and strips them for you.