How to Convert Decimal to Hexadecimal

The digits

Base 16 needs sixteen symbols, so after 9 it continues with the letters A to F.

Decimal:  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hex:      0 1 2 3 4 5 6 7 8 9 A  B  C  D  E  F

Method: repeated division

Divide the number by 16, write down the remainder, then divide the quotient by 16 again. Stop when the quotient is 0. The hex number is the remainders read from last to first.

3054 / 16 = 190 remainder 14  (E)
 190 / 16 =  11 remainder 14  (E)
  11 / 16 =   0 remainder 11  (B)

read backwards: BEE   ->   3054 = 0xBEE

255 / 16 = 15 remainder 15 (F), 15 / 16 = 0 remainder 15 (F)  ->  FF

Check it by converting back

Multiply each digit by a power of 16 and add: BEE = 11 * 256 + 14 * 16 + 14 = 2816 + 224 + 14 = 3054.

Code

JavaScript numbers lose precision above 2^53 - 1 (9007199254740991), so use BigInt for large values.

// JavaScript
(255).toString(16);              // "ff"
parseInt("ff", 16);              // 255
BigInt("18446744073709551615").toString(16);   // "ffffffffffffffff"

# Python
hex(255)                         # "0xff"
int("ff", 16)                    # 255

// C#
255.ToString("X");               // "FF"
Convert.ToInt32("FF", 16);       // 255

Negative numbers and prefixes

Use the Decimal to Hex Converter for quick checks, or the Number Base Converter to see binary, octal, decimal and hex together.

• Hex has no sign of its own. Negative integers are shown in two's complement for a fixed width: -1 as a 32-bit value is FFFFFFFF.
• Code usually writes hex with a prefix: 0xFF in C, C#, Java and JavaScript, #FF in CSS colours.
• Pad to a fixed width when you need it, for example 0A rather than A for one byte.