Convert hexadecimal to decimal and back: guide and table
Convert hexadecimal numbers to decimal, binary and octal. Understand base 16 with CSS and computing examples.
Published on January 13, 2026Hexadecimal notation (base 16) is ubiquitous in computing: CSS color codes (#FF5733), memory addresses, register values, MD5/SHA hashes and network protocols. Knowing how to convert between hexadecimal and decimal is an essential skill for developers and IT professionals.
Understanding the conversion
Base 16 uses digits 0–9 and letters A–F (A=10, B=11, C=12, D=13, E=14, F=15). Each hexadecimal digit represents 4 bits (a half-byte, called a nibble). Two hex digits therefore represent a complete byte (0–255 in decimal). To convert hex → decimal, multiply each digit by the corresponding power of 16 at its position. For decimal → hex, repeatedly divide by 16 and read remainders upward.
📐 Formula
📊 Conversion table
| Hexadecimal | Decimal | Binary | Common use |
|---|---|---|---|
| 0x00 | 0 | 00000000 | Null value |
| 0x0F | 15 | 00001111 | Max low nibble |
| 0xFF | 255 | 11111111 | Max byte, CSS opacity |
| 0x1F4 | 500 | 111110100 | Generic value |
| 0xFFFF | 65,535 | 16 bits all 1 | Max network port |
| #FFFFFF | R:255 G:255 B:255 | — | White in CSS |
| #FF0000 | R:255 G:0 B:0 | — | Red in CSS |
💡 Practical examples
R = 0x3A = 3×16+10 = 58. G = 0x7B = 7×16+11 = 123. B = 0xD5 = 13×16+5 = 213. rgb(58, 123, 213) — a medium blue.
255 ÷ 16 = 15 remainder 15 (F). 15 ÷ 16 = 0 remainder 15 (F). Read from bottom to top: FF. 255 decimal = 0xFF.
0x7FFF0000 = 7×16⁷ + F×16⁶ + F×16⁵ + F×16⁴ + 0×... = 2,147,418,112 in decimal. 64-bit memory addresses are far more readable in hex than decimal.