Thirteen times. That's how many times students from St Mark's School in Southborough, Massachusetts managed to fold it as part of their studies. That's right, kids are actually going to school to learn how to fold TP.
It's not all fun and games though. Turns out there's actually mathematics involved. From New Scientist:
Based on the thickness of a sheet of paper, a formula can be used to calculate the minimum length needed to fold it a given number of times. Paper roughly doubles in size with each fold and the sides become more rounded, making it harder and harder to bend. Wrinkles also have a significant impact, making the formula difficult to follow in practice. In addition, no single roll is long enough to fold thirteen times, requiring the group to tape together numerous rolls of industrial toilet paper 1.2 kilometers long.
The final result was 1.5m wide, 76cm high and consisted of 8192 layers of paper. The 13 folds beat the previous record of seven times comprehensively.