Hex to Decimal Converter

Hexadecimal (base 16) is how programmers write bytes, memory addresses, error codes and colors compactly: two hex digits always describe exactly one byte. This converter turns a hex value into decimal and shows the sum it used, so you can check the result or learn the method. The same value also appears in binary and octal.

How to use the hex to decimal converter

1. Type or paste the hex number. A 0x prefix is optional, and spaces and underscores are ignored, so 0xDEAD_BEEF and DE AD BE EF both work.
2. Leave Convert from set to hex. You can switch it to binary, octal or decimal at any time.
3. Read the decimal result, along with the binary and octal forms of the same number.
4. Check the step-by-step working under the result: each digit times its power of 16.
5. Use the copy button next to any result to copy it.

How it works

Each position in a hex number is worth 16 times the position to its right. The letters A to F stand for the digit values 10 to 15. To convert, multiply every digit by 16 raised to its position (counting from 0 on the right) and add everything up:

decimal = dₙ × 16ⁿ + … + d₂ × 16² + d₁ × 16¹ + d₀ × 16⁰

Hex digit	0–9	A	B	C	D	E	F
Value	0–9	10	11	12	13	14	15

Position	16⁰	16¹	16²	16³	16⁴
Place value	1	16	256	4,096	65,536

The converter does this with JavaScript’s BigInt, which stores whole numbers of any size exactly, so a 64-bit or 128-bit value converts without rounding. Fractions such as 0.8 in hex aren’t supported.

Worked examples

FF → 255

F × 16¹ + F × 16⁰ = 15 × 16 + 15 × 1 = 240 + 15 = 255. In binary that is 11111111: eight ones, one full byte.

1A3 → 419

1 × 16² + A × 16¹ + 3 × 16⁰ = 1 × 256 + 10 × 16 + 3 × 1 = 256 + 160 + 3 = 419.

0x7FFFFFFF → 2,147,483,647

7 × 16⁷ + F × (16⁶ + 16⁵ + … + 16⁰) = 7 × 268,435,456 + 15 × 17,895,697 = 1,879,048,192 + 268,435,455 = 2,147,483,647. That’s the largest signed 32-bit integer, a value you’ll see as an upper limit in many programs.

FFFFFFFFFFFFFFFF → 18,446,744,073,709,551,615

Sixteen F digits are 64 one-bits, so the result is 2⁶⁴ − 1, the largest unsigned 64-bit integer. A regular JavaScript number can’t hold this exactly; BigInt can.

Hex to decimal quick reference

Hex	Decimal	Hex	Decimal
0A	10	80	128
0F	15	FF	255
10	16	100	256
1F	31	3E8	1,000
2F	47	400	1,024
64	100	FFFF	65,535

Related guides

• Converting a binary number instead? Use the binary to decimal converter, or go the other way with decimal to binary.
• Web colors like #FF5733 are three hex bytes: the hex to RGB converter turns them into red, green and blue values.
• Print numbers as hex in Java with the %x conversion, explained in our Java printf guide.