Hex to Decimal Converter (and Decimal to Hex)

About this tool

Paste a hex value and get its decimal equivalent, or type a decimal number and get hex back. Next to the two fields, the tool lists the binary bits in groups of four, reads the value as a signed integer of the width you choose, splits it into bytes in both big-endian and little-endian order, and writes out the arithmetic. It works on whole numbers of any length thanks to JavaScript BigInt, so 64-bit hashes and long IDs convert without rounding. Need to turn a string of text into hex byte codes instead? That is what the Text to Binary and Hex converter does. This page treats the input as one number.

How to convert hex to decimal here

1. Enter the hex value in the Hexadecimal field. 0x1F, 1f, #1F and 1F all mean the same number.
2. The decimal result appears straight away. Type in the Decimal field to go the other way.
3. Choose 8, 16, 32 or 64 bits to match the variable or register you are reading. The box below shows the signed value and the byte order for that width.
4. Use the step-by-step box to check your own hand calculation.

Why one hex digit equals four bits

Hexadecimal is base 16, and 16 = 2⁴. Four bits have exactly 16 possible patterns, from 0000 to 1111, and hex has exactly 16 digits, 0 to 9 then A (10) to F (15). So every hex digit maps to one fixed group of four bits with no carrying between groups, and a byte (eight bits) is always two hex digits. That is the whole reason hex is so common in computing: it is a compact way to write binary that you can still convert in your head. The default value shows it: FF9C is 1111 1111 1001 1100, one group per digit.

Worked example: FF9C to decimal

Each place in a hex number is worth a power of 16, counting from 0 on the right. Multiply each digit’s value by its place and add:

The sum is 61,440 + 3,840 + 144 + 12 = 65,436. Going back from decimal to hex, divide by 16 and keep the remainders: 65,436 ÷ 16 = 4,089 remainder 12 (C); 4,089 ÷ 16 = 255 remainder 9 (9); 255 ÷ 16 = 15 remainder 15 (F); 15 ÷ 16 = 0 remainder 15 (F). Reading the remainders from last to first spells FF9C.

If those two bytes hold a signed 16-bit integer, the answer is different. A 16-bit pattern whose top bit is set stands for its unsigned value minus 65,536, so FF9C read as signed is 65,436 − 65,536 = -100. The same bits, two meanings: the program reading them decides which, so pick the width that matches your data type.

Where you meet hex numbers

• Web colors. #FF8800 is three bytes: red FF = 255, green 88 = 136, blue 00 = 0. The three-digit form doubles each digit, so #F80 is the same color. Converting the whole string to one number (16,746,496) is rarely what you want for a color; the Color Converter gives RGB and HSL.
• Memory addresses and debugging. Debuggers, crash logs and hex dumps print addresses and raw bytes in hex. A 32-bit value tops out at FFFFFFFF = 4,294,967,295.
• Unicode code points. Characters are numbered with U+ and hex digits: U+00E9 (é) is 233 and U+1F600, the grinning face emoji, is 128,512. The last code point, U+10FFFF, is 1,114,111.
• MAC addresses. A network card’s EUI-48 address is six bytes written as hex pairs, such as AC-DE-48-23-45-67. Paste it here, hyphens and all, to see it as the single 48-bit number 190,070,692,988,263.
• Hashes and IDs. Output from the Hash Generator and the digits of a UUID are hex.

Byte order

Byte order only matters once a number is stored in memory or a file as several bytes. Big-endian puts the most significant byte first, so the 16-bit value FF9C is stored as FF 9C. Little-endian, the order x86 processors use, stores the same value as 9C FF. If a hex dump shows 9C FF and you convert it as written, you get 40,191 instead of 65,436. Reverse the byte pairs (not the single digits) first.

Common mistakes

• Reading hex 10 as ten. 0x10 is 16. Likewise 0x100 is 256.
• Mixing up the letter O with zero, or I with 1. Hex digits stop at F, so G to Z are never valid.
• Reversing digits instead of bytes. Swapping byte order turns 12 34 into 34 12, not 43 21.
• Calling a value negative without a width. FF is −1 only as a signed 8-bit value; as a 16-bit value it is 255.
• Expanding the three-digit color form as a number. #F80 is 3,968 as an integer, but the color it names is #FF8800.

Sources: MDN on CSS hex colors, the Unicode UTF and BOM FAQ for the code point range, and the IEEE EUI guidelines for MAC address notation.