How to Calculate Ovulation Date

By calculating your ovulation date, you can determine the best times to have sex when trying to conceive.

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The most fertile time during the menstruation cycle is during ovulation—when the ovaries release a mature egg that travels through the fallopian tubes. The egg stays in the reproductive tract for about 12-24 hours, and if it becomes fertilized with sperm during that time, a person can become pregnant. Here are some tips for calculating your own ovulation cycle.

Ovulation and Fertility

After the egg is released, it survives for about 12-24 hours. However, sperm can live from three-five days in the reproductive tract, according to Staci Pollack, M.D., an OB-GYN for the Division of Reproductive Endocrinology & Infertility at Montefiore Health System. Therefore a person can conceive by having unprotected sex five days before ovulation (though the odds are highest on the day of ovulation and one day prior).

It is important to remember that you can also get pregnant outside your ovulation window. Factors such as having erratic periods, your ovulation timing changing month-to-month, and the sperm's ability to live for up to five days can spell a positive on that pregnancy test.

When is My Ovulation Date?

Most people of child-bearing age ovulate about 14 days into their menstrual cycles (if you count the first day of your period as day one), according to Sharifa Menon, M.D., F.A.C.O.G, an OB-GYN at Westchester Medical Center, the flagship of the Westchester Medical Center Health Network (WMCHealth). For a rough estimate of your ovulation date, subtract 14 from the date you expect your next period to begin. Here are some ovulation date examples:

  • If your period is due on the 30th of the month, you'll probably ovulate on the 16th. (And your five-day fertile window is the 11th through the 16th).
  • If your period is due on the 21st of the month, you’ll probably ovulate around the 7th. (And your five-day fertile window is the 2nd through 7th).

However, the ovulation date depends on the length and regularity of your menstrual cycle—and it can be harder to tell when you're ovulating if your cycle varies from month to month.

Ovulation Date Calculator Methods

Although every person who menstruates should learn to track their cycle, including ovulation windows, you can also calculate your ovulation date with other methods. Here are a few to learn more about.

Ovulation Predictor Kits (OPKs)

The most accurate way to know when you're ovulating is to use an ovulation predictor kit (OPK). These work by detecting a surge in luteinizing hormone (LH), which your body releases up to two days before you ovulate. Because these kits give you the most advance warning, they're your best bet for knowing when to time sex to coincide with ovulation.

Basal Body Temperature

Your basal body temperature (your body's temperature first thing in the morning) increases slightly—about half a degree —when ovulation occurs. Because this spike is so small, you need a special basal body thermometer to measure it. A BBT thermometer is more sensitive than a regular thermometer and can detect temperature changes as slight as tenths of a degree.

Vaginal Discharge

Your vaginal discharge can help predict your ovulation date as well. Most people have a clear and somewhat elastic, egg white-like (try stretching it between two fingers) discharge in the days leading up to ovulation.

Ovulation Symptoms

Some physical symptoms may accompany ovulation, but they're subtle enough that not everyone can spot them. About 20 percent of women experience lower abdominal pain (it's called mittelschmerz) when ovulation occurs. Breast tenderness is also common.

Doctor Visit

With blood tests and pelvic ultrasounds, doctors can monitor your ovulation cycle, says Jingwen Hou, M.D., Ph.D., an Ob-Gyn specializing in reproductive endocrinology and infertility at Kaiser Permanente in Hawaii. A trip to the doctor's office can also help answer any questions about conceiving, including any concerns about infertility.

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