Number Base Converter
Convert between binary, octal, decimal, hex and any base from 2 to 36.
How to use Number Base Converter
- Type a number.
- Choose the base it is written in.
- Read it in binary, octal, decimal, hexadecimal, base 36 and a base of your choice.
How it works
Conversion uses arbitrary-precision integers (BigInt), so numbers of any length convert exactly, beyond the 53-bit limit of ordinary JavaScript numbers. Prefixes such as 0x, 0b and 0o are accepted, and spaces or underscores used as digit separators are ignored.
Binary output is grouped in 4-bit nibbles and hexadecimal in bytes, which makes bit patterns easier to read. Negative numbers keep a minus sign; two’s-complement representation is not applied.
Example
Decimal 255 is 1111 1111 in binary, 377 in octal and FF in hexadecimal.
Frequently asked questions
How do I convert binary to decimal by hand?
Multiply each bit by 2 raised to its position from the right (starting at 0) and add them: 1011 = 8 + 0 + 2 + 1 = 11.
Does it handle very large numbers?
Yes. There is no fixed size limit because it uses arbitrary-precision integers.
Can I convert fractions like 0.5?
No, only whole numbers are supported.
What digits are used above base 10?
Letters a–z for 10–35, case-insensitive (so base 16 uses 0–9 and a–f).
Limitations
- Whole numbers only.
- Negative numbers are shown with a minus sign, not in two’s complement.
Last reviewed November 9, 2026. How we build and test tools.