What is a hexadecimal number in decimal?

How it works

A base says how many digits a numbering system has, and each place is worth that many times the one to its right. In decimal the places are ones, tens, hundreds. In binary they are ones, twos, fours, eights. In hexadecimal, which has 16 digits (0–9 and A–F), they are ones, sixteens, 256s and so on. Computers use binary, and hexadecimal is a compact way to write it: one hex digit is exactly four binary digits.

To convert, add up each digit times the value of its place. For example hex FF is 15 × 16 + 15 = 255, which is 11111111 in binary and 377 in octal. Going the other way, divide by the new base again and again and read the remainders backwards (Knuth, The Art of Computer Programming, vol. 2, section 4.1).

This tool works with whole numbers of any size, so a 64-bit or even larger value stays exact, and accepts bases from 2 to 36, where the letters a to z are the digits ten to thirty-five. You can type spaces or underscores to group digits, a minus sign, and the usual 0x, 0b and 0o prefixes. Fractions are not converted.