What does a ouvlation catulater do ?

Fertile window: If you are trying to get pregnant, an ovulation calculator and help you find the time of the month you are most likely to ovulate (and get pregnant). If you are trying to avoid pregnancy, it helps you know when to avoid intercourse. They aren't perfect but do give you some idea of timing. There are apps for smart-phones and internet sites that do this for you. Good luck!

Ovulation: A calculator will help predict when you will release an egg, however, not an exact time. Ovulation kits using urine predict within a 24-36 hour window.