Ovulation Calculator

The ovulation calendar predicts the approximate dates when you may ovulate and be fertile, and is intended for use by those with regular menstrual cycles.

Member? login and your tracking history fills in last period and cycle length fields below!

Step 1. Ovulation Calculation Rule

Your ovulation cycles will be calculated using the data specified below.


Step 2. Ovulation Calendar Display

Calendar Date Book

Important: The information on this ovulation calendar should not and cannot be used to prevent pregnancy.

How the Ovulation Calculator Works

Based on the first day of your last period, the average number of days in your menstrual cycle, and your average luteal phase length, the ovulation calculator forecasts your ovulation and fertile days. The predicted ovulation date and fertile days in each menstrual cycle are approximate dates only; this ovulation calculator is intended for use by those with regular cycles. The Advanced Ovulation Calculator at our site WhenMyBaby.com can be helpful if your cycles vary.

The luteal phase of the menstrual cycle is the number of days between ovulation (release of an egg from the ovary) until the day before your next menstrual period starts. For many women with regular menstrual cycles, the luteal phase is generally from 10 to 16 days, with 14 days being the average length. If you know your luteal phase length - because you've either charted your fertility cycles in the past, or have used ovulation prediction kits - you can specify it in the entry field on the criteria screen; you can also use MyMonthlyCycles Luteal Phase Calculator to calculate your luteal phase length.

To calculate the approximate ovulation date for a given cycle, the calculator does the following:

  1. It calculates the first day of your next menstrual cycle. That is, the day when your next period begins. This calculation is performed by adding your cycle length to the first day of last menstrual period (LMP).

    For example, if the first day of your last period was July 1, and your cycle length is 29 days, your next period would begin on or about July 30th.

  2. Next, the calculator subtracts your luteal phase length from the first day of your next period, yielding the approximate date of ovulation in the current cycle.

    Continuing the above example, if your luteal phase length is 14 days, it would subtract 14 from July 30th. The result, July 16th, is the approximate date of ovulation for the cycle that began on July 1st.

The fertile days are calculated based on the following: male sperm can live from 3 to 5 days in fertile cervical mucus. A female egg, once ovulated, can survive for up to 24 hours.

As a result, you are likely fertile a few days before ovulation, up to and including the day of ovulation, and for 12 to 24 hours thereafter, as shown on the resulting chart.

More Ways to Determine Ovulation

While the ovulation calculator can be very helpful, there are also other ways to determine and your fertile days, including:

Talk to your healthcare provider or medical doctor about which methods are best for you.

Disclaimer: The information on this ovulation calendar should not and cannot be used to reliably prevent pregnancy. This ovulation calculator is not intended for those having irregular menstrual cycles; if your cycle is irregular, talk to your healthcare provider regarding methods that can help determine your fertility cycles. Even if your cycles are regular, we make no guarantee that your period, ovulation, and/or fertile days will occur on the predicted dates shown on the calculated ovulation calendar, since each person's menstrual and fertility cycles can vary in any given month for a variety of reasons.

All information provided on this ovulation calculator, including predicted dates of menstruation, ovulation and fertile days, is for educational purposes only. It is not intended as a substitute for advice provided by a medical doctor or qualified healthcare provider. You should not use this information for self-diagnosis or for treating a health problem or disease. If you have any questions whatsoever about your medical health or believe you have a medical problem or disease, you should contact your medical doctor or healthcare provider.