Hex to Decimal Converter

How to convert hex to decimal

1. Write down the hex number and number each digit's position from right to left, starting at 0.
2. Multiply each digit's value (0-9 = 0-9, A-F = 10-15) by 16 raised to the power of its position.
3. Add all the results together — that's your decimal number.

Example: 1A3₁₆ = (1 × 16²) + (10 × 16¹) + (3 × 16⁰) = 256 + 160 + 3 = 419.

Background reading: the hexadecimal system on Wikipedia.

int("FF", 16)      # → 255

parseInt("FF", 16);   // → 255

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    long v = strtol("FF", NULL, 16);
    printf("%ld\n", v);  /* → 255 */
    return 0;
}

Real-world applications

• Reading HTML color codes like #FF5733, where each hex pair sets a red, green or blue channel.
• Interpreting memory addresses, error codes and crash dumps in debuggers.
• Working with MAC addresses and IPv6 addresses in networking.
• Writing binary data compactly — one hex digit replaces four bits.

Common mistakes

• Forgetting that A–F mean 10–15, not 1–6.
• Reading hex as decimal — 10₁₆ is sixteen, not ten.
• Ignoring the 0x prefix: 0x10 and plain 10 are different numbers.

Frequently asked questions

Need the reverse? Try our decimal to hex converter.