There is no universal number; permitted stays on tourist visas commonly range from two weeks to ninety days per visit depending on the country and your nationality, with some countries granting six months to certain passports. The figure that governs you is printed on the visa or stamped on entry, and that stamp is the authority, so photograph it on arrival and diarise the exit deadline.
A few subtleties catch people out. Some visas state both a validity window (when you may use the visa) and a maximum duration per stay, which are different things. Others cap total days within a rolling period, so leaving and re-entering does not reset the clock. And officers sometimes grant fewer days than the maximum, which is why checking the stamp before leaving the counter matters.
Overstaying, even briefly, can mean fines and bans that surface years later on unrelated applications, so build in buffer days rather than flying out on the final date. Check the official immigration website for your passport's exact allowance.