Converting hexadecimal (base 16) to base 10 is easy. The numbers 0-9 in base 10 are the same in base 16. But the numbers 10-15 in base 10 is actually letters when in base 16: 10-A, 11-B, 12-C, 13-D, 14-E, 15-F.

HEXADECIMAL 0 1 2 3 4 5 6 7 8 9 A B C D E F
DECIMAL 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15