Number Base Converter
Convert numbers between binary, octal, decimal and hexadecimal.
Results update as you type.
About this calculator
A number base converter rewrites an integer from one positional base to another — binary (base 2), octal (base 8), decimal (base 10) and hexadecimal (base 16). It reads your value in the source base, computes its decimal value, and re-expresses it in the target base.
Frequently asked questions
How do I convert decimal to binary?
Repeatedly divide by 2 and read the remainders from bottom to top. For example 10 in decimal is 1010 in binary, and 255 is 11111111.
What is hexadecimal used for?
Hexadecimal (base 16) packs four binary bits into one digit (0–9 then A–F), so it is a compact way to write bytes. The decimal number 255 is FF in hex.
Why does my number show a dash?
The digits must be valid for the source base — for example only 0 and 1 in binary, or 0–9 and A–F in hex. An invalid digit makes the result undefined.
Results are estimates for general guidance only, not financial, medical or tax advice.