How to Calculate Fertile Time

A woman's ovary releases an egg about 14 days before the beginning of each menstrual period in a process called ovulation. Between periods, there is a fertile time during which a woman may be more likely to conceive. If you have regular cycles that typically last between 28 to 32 days, you can calculate approximately when your fertile time occurs. Women who have irregular periods may use an at-home test kit instead. Since these calculations are not infallible, use them to help conceive a baby, but not as an effective means of birth control.

Things You'll Need

• Ovulation predictor test

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Instructions

• 1

  Write down the date that your period begins. This is the first day of your monthly cycle.

• 2

  Count forward 11 days and write down this date. This is typically the first day of ovulation.

• 3

  Count forward to day 21 from the first day of your cycle. This is typically the last day of ovulation for many women. Days 11 through 21 are the "fertile phase" of your cycle.

• 4

  Try to have intercourse between days seven and 20 of your cycle if you are trying to conceive a baby. Having sex just before your fertile period can increase your chances of pregnancy, because sperm lives for an average of three to five days inside your body, whereas your released eggs can only become fertilized for 12 to 24 hours.

• 5

  Use an at-home ovulation predictor test to calculate your fertile time if you have irregular periods. This test evaluates your urine to detect surges in a certain hormone which indicates whether or not you will ovulate soon. Test your urine for several days around the time when you think you may ovulate, or 11 days after your first day of menstruation. Different brands of test kits will provide different instructions for interpreting the results of the urine test stick.