Number Base Converter

What this tool does

A CSS colour is FF2A55, a permissions mask is 0755, a network dump shows 0xC0A80101, and a firmware register is described in binary. All four are the same kind of number written in different bases, and converting them by hand is where off-by-one errors creep in. This tool takes a number in whichever base you have and shows it instantly in decimal, hexadecimal, binary, octal and any custom base from 2 to 36. It also reports the bit width, which answers a practical question before you write a value into a field: will this fit in a byte, a 16-bit word or a 32-bit integer. Developers use it when reading flags, checking memory addresses, interpreting error codes, or preparing test vectors for a parser.

How to use it in three steps

1. Pick the base of the number you already have, then type it. Prefixes such as 0x are best removed so the input matches the base you selected.
2. Every other base updates instantly; copy the one your target expects. Check the bit width if the value is going into a fixed-size field.
3. Use the custom base field for bases such as 32 or 36 when you are working with compact identifiers or encoded counters. Check the bit width against the field you are writing to before treating a converted value as final.

Questions people ask

Why does a hexadecimal value sometimes turn into a negative number?

That happens when the value is interpreted as a signed integer of a fixed width rather than as an unsigned one. Check the bit width and the convention of the system you are reading from before treating it as negative.

What is the bit width figure for?

It tells you how many binary digits the value needs, which is the quickest way to see whether it fits in an 8-bit byte, a 16-bit word or a 32-bit field. A value wider than the target field will be truncated or rejected.

Can it convert fractional numbers?

No. It handles whole numbers only, which covers addresses, masks, flags and identifiers. Fractions require a different representation and are outside what this tool does.

Why do bases above 10 use letters?

A single digit has to represent a value larger than nine, so base 16 uses A through F and base 36 uses the alphabet up to Z. Those letters are digits in that notation, not labels; base 36 is popular for compact counters because it uses the whole alphabet.

Privacy: All base conversions and bit-width calculations are computed locally in this browser tab, so values taken from memory dumps, device registers and internal identifiers stay entirely on your machine.