Number base converter

What it does

A hex to decimal converter, and the other way round, is what you reach for when reading colour codes, memory addresses, file permissions, Unicode code points or hashed IDs. Type a number in any base from 2 to 36 and the binary, octal, decimal and hexadecimal forms appear at once, along with one extra base of your choosing. Values can be as large as you like and negative numbers are supported. Digit grouping, uppercase letters and 0x-style prefixes are options, so the output can be pasted into code, a spreadsheet or a document without editing.

How to use it

1. Type the number. Prefixes such as 0x, 0b and 0o are accepted, and spaces, commas and underscores are ignored.
2. Set the input base. It defaults to 16 for hexadecimal.
3. Pick an extra output base if you need something other than the four common ones.
4. Toggle grouping, uppercase and prefixes to suit where the value is going, then copy the line you need.

How to read the result

The default input FF3A in base 16 converts to 65,338 in decimal, 1111 1111 0011 1010 in binary and 177 472 in octal. The binary is grouped in fours because each group of four bits is exactly one hex digit: 1111 is F, 0011 is 3, 1010 is A. The "Bits needed" stat reads 16, and the hint says the value fits in 32 bits, so it is safe in any integer type.

Hex digits are grouped in pairs because each pair is one byte; the "Bytes" stat of 2 reflects that. Decimal output is grouped in thousands with commas for readability, which you can switch off when pasting into code.

If the input contains a digit that does not exist in the chosen base, such as 9 in binary or G in hex, a red message names the character rather than guessing. For a colour such as #1E90FF, convert each pair separately to get the red, green and blue values of 30, 144 and 255.

Low-level details like these come up in web app development more often than people expect. For colours specifically, the color converter handles hex, RGB and HSL together.