Common Mistakes When Converting Hex, Decimal and Binary
Most hex, decimal and binary errors come from five slips: dropping leading zeros, using an odd number of hex digits, leaving prefixes like 0x or #, confusing the letters A–F with numbers, and mixing up a digit character with its value. Converting digit by digit in 4-bit groups prevents almost all of them.
The one table you need
| Hex | Binaire | Décimal | Hex | Binaire | Décimal |
|---|---|---|---|---|---|
| 0 | 0000 | 0 | 8 | 1000 | 8 |
| 1 | 0001 | 1 | 9 | 1001 | 9 |
| 2 | 0010 | 2 | A | 1010 | 10 |
| 3 | 0011 | 3 | B | 1011 | 11 |
| 4 | 0100 | 4 | C | 1100 | 12 |
| 5 | 0101 | 5 | D | 1101 | 13 |
| 6 | 0110 | 6 | E | 1110 | 14 |
| 7 | 0111 | 7 | F | 1111 | 15 |
Mistake 1: Dropping leading zeros
✕✓💻 Hex 5 is 0101, not 101. When you join groups, missing zeros shift every bit after them. Always write each hex digit as exactly four bits, and each byte as eight.
Mistake 2: An odd number of hex digits
✕✓Our Hex to Binary converter reads hex in pairs – one byte per pair. If you enter a single digit like F, it is read as F0 and gives 11110000. Pad it to 0F to get 00001111.
Mistake 3: Leaving prefixes and symbols
✕✓Remove 0x from programming values (0x1F → 1F) and # from colour codes (#FF5733 → FF5733). Spaces between bytes are fine for reading, but strip other characters.
Mistake 4: Treating A–F as letters
In hex, A to F are digits worth 10 to 15. "1A" is 26 in decimal (1 × 16 + 10), not "1 and a letter". Converting 1A to binary gives 0001 1010.
Mistake 5: Digit character vs value
The character "5" typed in text is stored as 00110101 (ASCII 53), while the number 5 is 00000101. Use Text to Binary for characters and Decimal to Binary for numeric values.
A safe method every time
- Remove prefixes (0x, #) and spaces.
- Make sure the number of hex digits is even – add a leading 0 if not.
- Replace each hex digit with its 4-bit group from the table.
- Check the total length is a multiple of 8.
- Verify with a converter – Binary to Hex should give back your original hex.
Open the Hex To Binary on pdfseotools.com – free, no sign-up and it works on any device.
Questions fréquentes
How do I convert hex to binary quickly?
Replace each hex digit with its 4-bit pattern: A = 1010, F = 1111, so AF = 10101111.
Why does F convert to 11110000 instead of 1111?
The Hex to Binary tool works in whole bytes (pairs of hex digits). A single F is treated as F0. Write 0F to get 00001111.
Are hex letters case-sensitive?
No. "ff" and "FF" mean the same value, 255.
Should I type 0x before hex numbers?
Remove prefixes such as 0x or # before converting – they are notation, not part of the value.
Why does my binary have the wrong length?
Leading zeros were dropped. Pad each byte to 8 digits (00000101, not 101) so groups line up.
What is the largest value in one byte?
FF in hex, 11111111 in binary, 255 in decimal.
Résumé
Four bits per hex digit, an even number of digits, no prefixes – and always check by converting back. All the converters are on the free binary converters page.
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