HEX to Decimal

Letters A to F, no prefix

The box accepts digits 0 through 9 and letters A through F, in either case. Spaces are not allowed. A 0x or # prefix fails. The error is Enter hexadecimal digits only. FF and ff both become 255. 10 becomes 16. An empty box fails the same test. The result is a base-10 string. This is not a color converter. A six-digit color still converts as one integer, which is rarely what a stylesheet wants. Use a color tool when you need red, green, and blue split apart.

Place value in sixteens

The rightmost digit is ones. The next is sixteens. A is 10, B is 11, C is 12, D is 13, E is 14, and F is 15. FF is 15 times 16 plus 15, which is 255. 100 is 256. You can check a two-digit value that way. Leading zeros do not change the number. 00FF is still 255. A very long hex string can lose low digits past the safe integer limit, the same JavaScript limit as the binary page, at 2^53 minus 1. Stay under that when the exact integer matters. B is 11, so 0B is 11. 20 is 32, which is two sixteens. Write the place values down once and a short hex string is the same multiply-and-add.

What the other base pages do

Decimal to Hex goes the other way and prints uppercase hex. Decimal to Binary and Binary to Decimal stay in base 2. Pasting 1101 here is legal hex, and it is not the binary value 13. Hex 1101 is 4353 in decimal. If your notes say binary, use the binary page. If your notes say FF, stay here. Binary Converter will treat the letters F and F as text and emit bit groups, which is a third, different result. Do not mix the three. If a homework line says convert FF, stay on this page. If it says convert 255 to hex, use Decimal to Hex. Swapping the titles produces a number that will not match the answer key.

A short check you can repeat

Type FF. The result is 255. Type 10. The result is 16. Type ff. The result is 255 again. Type 0xFF. You should see Enter hexadecimal digits only. Delete the 0x and run FF alone. Type a space. That fails too, unlike the binary page, which allows spaces. The value stays on this device. Copy the decimal if you need it in a spreadsheet. The page does not insert a thousands separator. Type B and expect 11. Type 100 and expect 256. If 100 comes back as 100, you are on a decimal page, not this one.