The luteal phase, which is often referred to as days past ovulation (DPO) begins on the day after ovulation and runs through until the day before menstruation. For information on how to calculate the length of your luteal cycle visit the Your Fertility section of the website. Don’t worry if you do not know this information yet. Simply leave the field blank and the calculator will put in average default values. However, we suggest that in the coming months you keep a record of your menstrual cycle so that you can adjust the values for cycle length or luteal phase at a later date.

There are approximately five fertile days during each menstrual cycle when sexual intercourse is most likely to result in pregnancy. These days are the date of ovulation and the four to five days prior to ovulation.

Because several factors can influence when ovulation occurs we recommend that the ovulation calculator be used in conjunction with other fertility testing and fertility awareness practices. See Common Methods for Predicting Ovulation for further details. This is particularly important if your menstrual cycle is irregular or if it its taking you longer to conceive than first anticipated.