Number Systems Converter

Convert any number between decimal, binary, octal and hexadecimal instantly.

How to Use This Converter

Enter a number, choose its base, and hit Convert to see all four representations.

Why do programmers use hex?

Hex maps cleanly to binary: each hex digit is exactly 4 bits, making byte values (00-FF) compact and readable.

How do I convert decimal to binary by hand?

Divide by 2 repeatedly, recording remainders from last to first. Example: 10 ÷ 2 → remainders 0,1,0,1 → 1010.

What is octal used for?

Legacy Unix file permissions (e.g. 755) and some old computing systems use octal because each digit is 3 bits.

Why is FF equal to 255?

F = 15. So FF = 15×16 + 15 = 255. It's the largest byte value, and the white color #FFFFFF.

Enter 255 with input base set to Decimal (base 10):

Binary — base 2, using only 0 and 1; the language of CPUs. Each digit is a bit.
Octal — base 8, using 0-7. Each octal digit represents exactly 3 bits, so 377 = 11111111.
Hexadecimal — base 16, using 0-9 and A-F. Each hex digit is exactly 4 bits, so bytes are written as two digits like FF.