Number Base Converter

Each hex digit is worth 16ⁿ where n is the position from the right (starting at 0). For 0xFF:

F × 16^1 = 15 × 16 = 240
F × 16^0 = 15 × 1  =  15
                    ----
                    255

For 0xDEADBEEF (32-bit integer, classic placeholder value):

D × 16^7 = 13 × 268435456 = 3489660928
E × 16^6 = 14 × 16777216  =  234881024
A × 16^5 = 10 × 1048576   =   10485760
D × 16^4 = 13 × 65536     =     851968
B × 16^3 = 11 × 4096      =      45056
E × 16^2 = 14 × 256       =       3584
E × 16^1 = 14 × 16        =        224
F × 16^0 = 15 × 1         =         15
                            ---------
                            3735928559

Every programming language has built-ins, of course:

// JavaScript
parseInt("DEADBEEF", 16)       // 3735928559
Number("0xDEADBEEF")           // 3735928559
(3735928559).toString(16).toUpperCase()  // "DEADBEEF"

# Python
int("DEADBEEF", 16)            # 3735928559
hex(3735928559)                # '0xdeadbeef'
f"{3735928559:X}"              # 'DEADBEEF'

// C / C++ / Go / Rust
// 0x prefix in source code → compile-time hex literal
int x = 0xDEADBEEF;

• Hex for: color codes (#FF6600), byte-level debugging, memory addresses, MD5/SHA hash output, network packets, binary file headers, Ethernet MAC addresses.
• Binary for: bit flags and bitmasks, explaining bit shifts, hardware registers, file format headers, protocol state machines. Modern CPUs operate on bytes (groups of 8 bits) so you rarely see pure binary outside embedded work.
• Octal for: Unix file permissions (chmod 755), string escape sequences (\777 in C). Rare outside these two.
• Decimal for: everything else, obviously. Humans.

Two's complement (how negative integers are stored) is where most people get stuck. -1 in 8-bit is 11111111 (all ones). The top bit is the sign bit in signed integers. Our converter has a two's-complement toggle to visualise both signed and unsigned interpretations.