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Hex to Decimal Converter
Convert hex to decimal with our free hex to decimal converter — or flip it and turn decimal numbers back into hex. Programmers, web designers and electronics students meet hexadecimal every day in color codes, memory addresses and error messages, and reading it means knowing its decimal value. This tool converts in seconds, with no sign-up, and also handles binary and octal.
How to use this converter
- Type the hexadecimal number in the Number box, for example FF. Letters A to F are fine in any case.
- Check that From is set to Hexadecimal and To is set to Decimal. Choose binary or octal if you need them.
- Read the answer in the result box. It updates as you type, and the line below shows both numbers with their bases.
- Use the Swap button to convert decimal back to hex without retyping.
Common values
| Hexadecimal | Decimal | Binary |
|---|---|---|
| 10 | 16 | 10000 |
| 1A | 26 | 11010 |
| 2F | 47 | 101111 |
| 64 | 100 | 1100100 |
| FF | 255 | 11111111 |
| 100 | 256 | 100000000 |
| 3E8 | 1,000 | 1111101000 |
How it works
Hexadecimal is a base-16 number system. Ordinary decimal counts in tens — each place is worth 10 times the one before it. Hex counts in sixteens: the places, reading right to left, are worth 1, 16, 256, 4,096 and so on. Because base 16 needs sixteen different digits, it borrows letters: after 9 come A, B, C, D, E and F, standing for 10, 11, 12, 13, 14 and 15.
To convert hex to decimal by hand, multiply each digit by the value of its place and add the results. FF has two digits: the right-hand F sits in the 1s place (15 × 1 = 15) and the left-hand F sits in the 16s place (15 × 16 = 240). Add them: 240 + 15 = 255. Longer numbers work the same way — 3E8 is 3 × 256 + 14 × 16 + 8 = 768 + 224 + 8 = 1,000.
The reverse trip, decimal to hex, uses repeated division by 16: divide the number, keep the remainder, and read the remainders from last to first, writing remainders of 10 to 15 as A to F. The converter above does both directions instantly and exactly, even for very long numbers, because it calculates with whole-number arithmetic rather than decimals.
Hex is everywhere in computing. Web colors are three hex bytes — #FF0000 is full red because FF (255) is the top of the red channel. Memory addresses, MAC addresses on network cards, IPv6 addresses and many error codes are all hex, and each hex digit maps neatly onto 4 binary digits, which is why engineers prefer it to long strings of zeros and ones.
Worked example
A web designer is checking a color code, #FF5733, and wants to know what the first byte, FF, means as an ordinary number.
Step 1: Write the hex digits with their values — F = 15 and F = 15.
Step 2: Multiply by the place values — the left F is in the 16s place: 15 × 16 = 240.
Step 3: The right F is in the 1s place: 15 × 1 = 15.
Step 4: Add them — 240 + 15 = 255.
So FF is 255, the maximum for one color channel, which is why #FF5733 starts with the strongest possible red. Going the other way, 255 divided by 16 gives 15 remainder 15, and then 15 itself — written as F and F — so 255 is FF in hex. Those are the exact results this converter gives.
FAQ
What is FF in decimal?
FF in hexadecimal equals 255 in decimal. F stands for 15, so FF = 15 × 16 + 15 = 240 + 15 = 255. It is the largest value one byte can hold and the brightest level in an RGB color.
What is 255 in hex?
255 in decimal equals FF in hex. Divide 255 by 16: you get 15 with remainder 15, and both 15s are written as F, giving FF. The decimal to hex converter above does it automatically, or use the swap button.
Why do computers use hexadecimal?
Hex is a compact way to write binary. One hex digit covers exactly 4 binary digits, so a full byte is just two hex digits (00 to FF). That is why memory addresses, MAC addresses, error codes and color codes like #FF5733 are written in hex.
What are the hex digits?
Hexadecimal counts in base 16, so it needs 16 symbols: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, then A = 10, B = 11, C = 12, D = 13, E = 14 and F = 15. Letters beyond F are not valid in a hex number.
What is hex 100 in decimal?
Hex 100 equals 256 in decimal, not one hundred. The places in hex are worth 1, 16 and 256, so 100 means 1 × 256 + 0 + 0 = 256. In the same way, decimal 100 is written as 64 in hex.
Can I convert decimal back to hex on this page?
Yes. Set From to Decimal and To to Hexadecimal, or press the swap button after a conversion. This page converts between decimal, binary, octal and hexadecimal in any direction.