When would I ovulate if my menustrals start on the 15?

Ovulation. In a typical 28 day cycle, ovulation happens on day 14. If you have 28-30 day cycles and menses started on the 15th, then ovulation will likely happen at the end of the month. To pinpoint the exact day, you can check ovulation predictor kits, starting testing daily on day 10 of your cycle.