Number base converter
Type a number in any base from 2 to 36 and read it in every other base at once. Exact for numbers of any size.
How positional bases work
In any base b, each place is worth b times the place to its right. In decimal the places are 1, 10, 100; in base 5 they are 1, 5, 25, 125. So 2435 = 2 × 25 + 4 × 5 + 3 = 73.
To go the other way, divide by the target base repeatedly and collect the remainders. The dedicated pages show every step for the common pairs: decimal to binary, hex to decimal, binary to hex, octal to decimal.
Negative numbers here keep a minus sign. If you need the bit pattern a computer uses for a negative integer, use the two's complement calculator.
Questions people ask
What is a number base?
The base (or radix) is how many digit symbols a system uses before it carries to the next place. Decimal has 10 (0–9), binary 2, octal 8, hex 16 (0–9 then A–F). Base 36 uses 0–9 and A–Z.
How do I convert between two unusual bases, such as base 5 to base 12?
Convert to decimal first (multiply each digit by powers of 5 and add), then divide the decimal value repeatedly by 12 and read the remainders upward. This converter does both steps at once for any bases from 2 to 36.
Why stop at base 36?
Ten digits plus 26 letters give 36 unambiguous single-character symbols. Beyond that you need case-sensitive letters or extra symbols, as Base64 does.
Where is base 36 used?
Short IDs and URL shorteners often use base 36 because it packs a large number into few characters while staying case-insensitive. JavaScript’s Number.prototype.toString(36) produces it.