A byte: FF
Hex
FF
Decimal
255
F × 16 + F × 1 is 15 × 16 + 15 = 240 + 15 = 255, the largest value one byte can hold.
Hex to Decimal Converter
Type a hexadecimal number and read its decimal value, with every step of the calculation shown underneath. It opens on FF, which is 255.
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How to convert hex to decimal
Hexadecimal is base 16. It uses the digits 0 to 9 and the letters A to F, where A is 10, B is 11 and so on up to F, which is 15. Each position is worth 16 times the one to its right: the rightmost digit counts ones, the next counts sixteens, then 256s, then 4096s.
To convert, take each digit's value, multiply it by its place value and add everything up. 2A is 2 × 16 + 10 × 1 = 42. 1F4 is 1 × 256 + 15 × 16 + 4 × 1 = 500. The panel under the converter writes out these lines for whatever you type.
The converter accepts upper or lower case and an optional 0x prefix, and it uses BigInt arithmetic, so values past 2⁵³ such as FFFFFFFFFFFFFFFF convert exactly.
What to know about hex numbers
- Hex digits run from 0 to 9, then A (10), B (11), C (12), D (13), E (14) and F (15).
- Place values are powers of 16: 1, 16, 256, 4096, 65536.
- Two hex digits make one byte, so they cover 0 to 255:
00is 0 andFFis 255. 0xin front of a number, as in0xFF, only marks it as hex. It is not part of the value.
Hex to decimal, worked out
A web color
Hex
#1E90FF
Decimal
rgb(30, 144, 255)
Each pair of digits is one color channel: 1E is 1 × 16 + 14 = 30, 90 is 9 × 16 = 144 and FF is 255.
Three digits: 1F4
Hex
1F4
Decimal
500
1 × 256 + 15 × 16 + 4 × 1 = 256 + 240 + 4 = 500.
A 16-bit limit
Hex
0x7FFF
Decimal
32767
7 × 4096 + 15 × 256 + 15 × 16 + 15 = 32767, the largest signed 16-bit integer.
Common hex to decimal mistakes
- Reading a letter as something other than a digit. In hex,
Ais 10 andFis 15, and no single digit is worth more than 15. - Counting positions from the left. The rightmost digit is position 0 and is worth 1.
- Multiplying by 10 instead of 16. Hex
10is sixteen, not ten. - Keeping the
0xor#prefix in the arithmetic. Drop it before converting.
Hex to decimal FAQ
What is FF in decimal?
255. Each F is 15, so FF is 15 × 16 + 15 = 255, the largest value that fits in one byte.
What is hex 10 in decimal?
16. The 1 sits in the sixteens place, so hex
10 is 1 × 16 + 0 = 16.How do I convert hex to decimal in Python or JavaScript?
In Python,
int('FF', 16) returns 255. In JavaScript, parseInt('FF', 16) returns 255; for values above 2⁵³ use BigInt('0xFF') so nothing is rounded.Why does hex use letters?
Base 16 needs sixteen single symbols and there are only ten digits. The letters A to F fill the six missing values, 10 to 15.
