The OPK Ovulation Predictor Calculator calculates when to start testing for the LH surge as well as your expected date of ovulation based on the first day of your last period and your cycle length. You can create your ovulation prediction kit (OPK) test calendar and schedule for your current and next menstrual cycle.

Enter information about your menstrual cycle, and the start cycle day to test per the instructions for the OPK you've purchased. Or, click your cycle length from the chart below which matches your OPK's instructions.