Ovulation Calculator

Free Online Ovulation Calendar

BabyHopes free ovulation calculator helps you figure out your most fertile days for getting pregnant.  If you are specifically hoping for a boy or a girl, we can give you suggestions based on Dr. Shettles recommendations.   

Calculating Your Menstrual Cycle Length

To calculate when you ovulate, you need to know how many days are in your menstrual cycle.  Your menstrual cycle length is the number of days between when your period started to the day before the next period starts.

If you already know your menstrual cycle length, scroll down and enter your information!

If you don't want to manually figure out the length, you can just click here. All you need is the start dates of your last two periods. We will calculate your cycle length for you.

Calendar Limitations

  • Cycle lengths of more than 35 days are too long for appropriate calculations.
  • Cycle lengths of less than 21 days are too short for appropriate calculations.
  • Fertility supplements can be helpful if your cycle is too short or long. They can balance your hormones and regulate the length of your cycle. The supplements also encourage regular ovulation.
  • Our calendar cannot be used to prevent pregnancy.

Calculate When You Are Most Fertile

First day of last menstrual period:
Length of cycle: days
Show me my most fertile days for: Months
Show me the best days to have sex in order to increase my chances of having a baby girl or baby boy.

Scroll down to see your most fertile days!


  • Helps you figure out the 4 most fertile days of your cycle.
  • Calculate your most fertile days for up to 3 months in the future.
  • Our ovulation calculator shows the best time to take a pregnancy test to find out if you are pregnant.
  • The BabyHopes ovulation calendar lets you calculate the best times to have sex, based on if you want to have a boy or a girl baby. The suggestions are based on Dr. Landrum Shettles book, "How to Choose the Sex of Your Baby"