Ovulation calculator | Free fertility calculator

How can you determine your "fertile time" so that you can plan baby-making sex? There are many methods that you can use to calculate the time you ovulate.

Menstrual period timing (Calendar method) To determine the length of the menstrual cycle, one only needs to note the date of the beginning of the menstrual period (first day of flow) for two consecutive periods, and then count the day from one date to the next. Keeping track of the length of menstrual cycles will help determine the approximate time of ovulation because the next period begins approximately two weeks from the date of ovulation.

The rough rule to calculate the approximate date of ovulation is: NMP minus 14 days, where NMP is the ( expected) date of the next menstrual period. This is because the luteal phase for most women is 14 days long.

Date of ovulation = NMP - 14

You can also use our Free Fertility Calculator at

Keeping track of the menstrual cycle by charting it can indicate ovulatory disturbances. For example, if a menstrual cycle that is normally 28 days starts to occur every 35 or 40 days, this may mean that ovulation is disturbed, and an evaluation is needed.
You can also use OPKs - ovulation prediction test kits, to monitor ovulation.

You can also track your cervical mucus to track ovulation. Combining this with the calendar method helps improve accuracy - and both are free!

Read more-Is BBT charting of any use for infertile couples

Authored by : Dr Aniruddha Malpani, MD and reviewed by Dr Anjali Malpani.