It actually depends on what is causing the ovulation pain, there is one kind that is caused by the growth of the follicle and another that is caused by the release of blood at the same time as the egg and another that is the rupture of the follicle itself. So it can be before, after or the moment of, which is really confusing and doesn't help you at all I'm afraid, but with my O pain which are strong cramps on one side and in my back lasted for two days and I o'd on the 2nd/last day of pain. Hope I was some help! Good Luck!