Our ovulation calculator is based around the following variables: the first day of your last period, your normal cycle length, and your luteal phase. The first two variables, the first day of your last period and your normal cycle length, are generally known. The length of your luteal phase can only be determined through specific hormone-centric blood tests. For this reason, we’ve set the default value of the luteal phase in the ovulation calculator to 14 days, which is the most common phase length.
The luteal phase is also known as your “days past ovulation” or “DPO” for short. This is the part of the cycle that begins with ovulation and terminates the day before your next period. Ovulation can be varied and delayed by a number of circumstantial factors such as stress, different medications, and many other reasons. Your luteal phase on the other hand is generally a constant from month to month regardless of what else is going on. The required phase length of a luteal phase to support pregnancy is generally 10 days. If you are looking for a more accurate ovulation calculation, you may consider having blood work done to determine your luteal phase. Otherwise we recommend sticking with the default 14 days phase length to estimate your best ovulation time span.
The result of this calculation will be a date range spanning several days. Your heavy ovulation days will be in the middle of this range. The first and last days of this time span are when ovulation is occurring but it is generally light ovulation. The heaviest ovulation day from this calculation will be the day right before the last day of the date range. For example, if your date range was January 11th through January 16th, typically the strongest ovulation day would be January 15th. To use the ovulation calculator simply enter the required information in the form fields and our calculator will let you know the best date rang for you to try to get pregnant.