Shitload means to have a lot of something, but the actual amount varies. To figure out how much is in a shitload you must follow a few steps.
1. pick an item - ex) pretzels
2. make it singular - ex) pretzel
3. figure out how many letters in in that word - ex) 7
4. multiply that number by 6 - ex) 7x6=42
5. it takes 42 pretzels to make a shitload of them!
It varies because if the word were short like car, it would be 3x6=18.