Hexadecimal to Decimal Converter

How to Convert Hex to Decimal

Each hexadecimal digit represents a power of 16. To convert:

1. Identify each hex digit (0-9, A-F where A=10, F=15)
2. Multiply each digit by 16^position (right to left, starting at 0)
3. Sum all the results

Example: Convert 0xFF to decimal:

• F (15) × 16¹ = 15 × 16 = 240
• F (15) × 16⁰ = 15 × 1 = 15
• Result: 240 + 15 = 255

Converting hex fractions to decimal

Type a point to convert a fraction: digits after it are worth 16^-1 = 1/16, 16^-2 = 1/256, and so on, so FF.8 is 255.5. A hex fraction always ends in decimal, because 1/16 is a finite decimal (0.0625), so the result here is always exact, never rounded.

Signed hex to decimal (two's complement)

The decimal result treats the input as an unsigned number. Computers usually store signed integers in two's complement, where the top bit carries a negative weight. To read hex as signed: if the first hex digit is 8-F, subtract 2ⁿ from the unsigned value, where n is the number of bits. So 80 is 128 unsigned but -128 as a signed 8-bit number. The converter shows this signed reading at the width you typed, so add leading zeros to widen it.

Other widths, and the full invert-and-add-one working, are on the two's complement calculator.

Code Examples

const hex = "ff";
const decimal = parseInt(hex, 16); // 255
// For large numbers, use BigInt:
const bigHex = "ffffffffffffffff";
const bigDecimal = BigInt("0x" + bigHex);

Frequently Asked Questions

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