What Is Hexadecimal?
By Mickael Gomes · Last updated: 2026-06-19
Hexadecimal is a base-16 number system. Where the decimal system we use every day has ten digits (0 through 9), hexadecimal has sixteen: the digits 0 through 9 followed by the letters A, B, C, D, E, and F, which stand for the values ten through fifteen. A single hexadecimal digit can therefore represent any value from zero to fifteen, and that one extra step of capacity is what makes hex so useful for working with computers.
How base-16 works
In any positional number system, each digit is worth its face value multiplied by the base raised to the power of its position. In decimal, the number 245 means two hundreds, four tens, and five ones, because the base is ten. In hexadecimal the base is sixteen, so each position is worth sixteen times the one to its right. The hex value 1F means one sixteen plus fifteen ones, which equals thirty-one in decimal.
Reading from the right, the place values are 1, 16, 256, 4096, and so on. This means a two-digit hex number covers 0 to 255, a three-digit number reaches 4095, and four hex digits span the full range of a 16-bit value, 0 to 65535. The pattern of multiplying by sixteen at every step is the whole of the system.
Why letters appear in numbers
The letters confuse people at first, but they are simply single symbols for values that decimal needs two digits to write. We cannot reuse "10" for the value ten inside a single hex digit, because "10" in hexadecimal already means sixteen. So the values ten through fifteen borrow the letters A through F. A equals ten, B equals eleven, and F equals fifteen. Case does not matter: FF and ff mean exactly the same value.
Where you see hexadecimal
Hexadecimal shows up wherever raw binary data needs to be written compactly. Web colors such as #FF8800 are hex. Memory addresses printed by a debugger, like 0x7FFE0000, are hex. Error codes, MAC addresses, cryptographic hashes, and the bytes shown in a hex editor are all hexadecimal. The reason is consistent: four binary bits map exactly onto one hex digit, so hex is a tidy shorthand for the binary that computers actually store.
You do not need to memorise conversions to benefit from hex. Recognising that a string of digits and the letters A–F is a number, and knowing roughly how big it is, is usually enough. When you need an exact value, a converter turns hex into decimal in an instant.