This question sounds simple, but the answer depends on the size and thickness of the paper.
For an ordinary sheet of paper folded by hand, the commonly quoted practical answer is about 7 times. Each fold doubles the thickness, so the paper becomes dramatically harder to bend with every attempt.
Answer: About 7 times for a typical sheet.
It is not an absolute law. Very large or specially prepared sheets can be folded more times, and the world record exceeds the usual classroom result. But for a normal piece of paper, seven folds is the familiar answer because thickness increases exponentially.
