What Is Hexadecimal?

Hexadecimal in one sentence

Hexadecimal is a positional number system with base 16: each digit is worth 16 times more than the digit to its right, and the values 10 to 15 are written with the letters A to F. To show that a number is hex, programmers write 0x1A (C, Java, JavaScript, Python), #1A2B3C for CSS colors, 1Ah in assembly or 1A₁₆ in mathematics.

Hex digits from 0 to 15

Counting in hex

Hex counts like decimal but carries over after F instead of after 9: … 8, 9, A, B, C, D, E, F, 10, 11 … 19, 1A … 1F, 20 … FF, 100. Here 10 means sixteen and 100 means 16 × 16 = 256. Two hex digits cover one byte (00–FF = 0–255), four digits go up to FFFF = 65,535 and eight digits up to FFFFFFFF = 4,294,967,295.

Why computers use hexadecimal

Computers store everything in binary, but long rows of 0s and 1s are hard for people to read and easy to mistype. Because 16 = 2⁴, one hex digit stands for exactly four bits (a nibble) and two hex digits for one byte. Converting between hex and binary is a simple digit-by-digit lookup, and hex is four times shorter: 1101 1110 1010 1101 is just DEAD. Decimal has no such neat relationship with binary, which is why it is rarely used for raw data.

Converting hex to decimal and back

• Hex to decimal: multiply each digit by its power of 16 and add: 2F = 2 × 16 + 15 = 47, and 1A3F = 1 × 4096 + 10 × 256 + 3 × 16 + 15 = 6719.
• Decimal to hex: divide by 16 repeatedly and read the remainders backwards: 200 ÷ 16 = 12 remainder 8, and 12 = C, so 200 = C8.
• Hex to binary: replace each digit with its 4 bits: 2F = 0010 1111.

Our converters do all of this instantly and show every step.

Where hexadecimal is used

• Web colors: #FF6347 is red FF, green 63 and blue 47.
• Memory addresses: debuggers and crash reports show pointers such as 0x7FFE5A3C.
• MAC addresses: six bytes such as 00:1A:2B:3C:4D:5E identify network cards.
• IPv6 addresses: eight groups of four hex digits, for example 2001:db8::1.
• Unicode: every character has a hex code point – U+00E9 is é and U+1F600 is 😀.
• Hashes and IDs: a SHA-256 hash is 64 hex characters, and UUIDs and Git commit IDs are written in hex.
• Hex dumps: hex editors show file contents byte by byte; every PDF starts with 25 50 44 46 (“%PDF”).
• Error codes: Windows reports errors such as 0x80070005 (access denied).

Hexadecimal, decimal, octal and binary compared

Negative numbers in hex

Hex itself has no special sign, so negative numbers are usually stored in two's complement: the highest bit of a fixed-size value marks it as negative. As a signed byte, 7F is 127, 80 is −128 and FF is −1; as a 32-bit integer, FFFFFFFF is −1. In math and in our calculator you can also simply write a minus sign: −1A = −26.

Updated: 2026-11-02