Number Base Converter
Enter a number in any base from 2 to 36 and see it in binary, octal, decimal and hexadecimal at once, plus any custom base you choose.
Binary · base 2
11111111
Octal · base 8
377
Decimal · base 10
255
Hexadecimal · base 16
ff
73
About this tool
Different bases suit different jobs: binary reflects how hardware stores data, hexadecimal compresses four bits into one readable character for colors and memory addresses, and octal survives in Unix file permissions.
Conversion uses arbitrary-precision integers, so values far beyond the usual 64-bit limit stay exact. That matters when working with large identifiers or cryptographic values where floating-point maths would silently round.
Frequently asked questions
- How do I convert decimal to binary by hand?
- Divide repeatedly by 2 and record the remainders, then read them bottom to top. 13 gives remainders 1, 0, 1, 1 — so 1101.
- Why is hexadecimal used so often in programming?
- One hex digit represents exactly four bits, so a byte is always two characters. That makes colors, memory addresses and binary dumps far easier to read than raw binary.
- What do prefixes like 0x and 0b mean?
- `0x` marks hexadecimal, `0b` binary and `0o` octal in most programming languages. The tool strips them automatically if you paste them.
- What is the largest base supported?
- Base 36, which uses the digits 0-9 followed by the letters a-z.
- Can it handle very large numbers?
- Yes. It uses BigInt arithmetic, so integers of any size convert exactly without rounding.