Ovulation Calculator and Fertility Calendar

Chances for pregnancy are usually best when sexual intercourse occurs 1 to 2 days before you ovulate.

Ovulation calculators and calendars are tools that attempt to predict when women might ovulate. These tools are based on the typical length of their menstrual cycle and the expected window for ovulation. These tools will guide women when they are releasing an egg each month (also known as ovulation) and when are they most fertile for the best chances of getting pregnant. Likewise, if they are taking any fertility medications, these tools can be used to suggest when they may be the most fertile for sexual intercourse. To use an ovulation calculator, women should know:

• When was the first day of their last menstrual cycle?
• Duration of their menstrual cycle
• The number of days in their luteal phase: This is the latter phase of the menstrual cycle starting from ovulation and ending just before bleeding starts. While the amount of time before ovulation can vary widely each month, the time after ovulation to the end of your cycle is usually fairly constant, and unless you have a health problem that affects your periods or you are pregnant, this phase lasts 14-16 days. If a woman is not sure about the length of the luteal phase, they can assume it is 14 days (the average length for most women).

Ovulation may sometimes vary depending on the menstrual cycle:

• If the average menstrual cycle of a woman is 28 days, then ovulation may occur around day 14, and the most fertile days are 12, 13, and 14.
• If the average menstrual cycles of a woman are 35 days, then ovulation may occur around day 21, and the most fertile days are 19, 20, and 21.
• If the average menstrual cycle of a woman is shorter or says 21 days, then ovulation may occur around day 7, and the most fertile days are 5, 6, and 7.

How to use this ovulation calculator tool

• Pick a date on the calendar that matches the day you started your last period
• The calendar will display your estimated ovulation date, marking it in red.
• The days leading up to your ovulation date will appear marked in purple; those are the days you are likely the most fertile.
• If you have records of how long your own menstrual cycle lasts, change the default number of 28 days in the dropdown menu in the results box for a more accurate calculation.

It is not advised. Some women try to use ovulation calculators and calendars as a form of natural birth control. The goal is to limit sex during predicted infertile days and abstain totally on fertile days as per the calendar. However, cycles may vary; average infertile days one month might become most fertile in the coming months. If women do not want to get pregnant, they should not totally rely on an ovulation calculator as a means of birth control. There is a significant risk that they may have an unwanted pregnancy.

Ovulation is the female reproductive process of releasing a mature egg from the ovaries and transferring it to the fallopian tubes for insemination. Generally, one egg is released every month, two weeks after menstruation begins. Below are a few common symptoms when a woman may be ovulating:

• Increased sex drive, especially during the mid of the cycle, maybe a common symptom of ovulating.
• Few women notice changes such as very little soreness in the breast about mid-way through the cycle, which may be a sign of ovulation. 
• Due to a surge in progesterone hormone, women’s basal body temperature may be increased by about 0.5° during ovulation, especially during resting. Keeping a track of basal temperature every morning may give the accurate fertile days in the month.
• Women may feel something happening in their ovaries around ovulation. These sensations may vary wildly and could be anything from mild aches to twinges of pain. Some women have a condition called Mittelschmerz, where they feel ovulation as a one-sided backache or a cramp. The feeling may last anywhere from a few minutes to a few days.
• Ovulating women usually notice a change in vaginal discharge (cervical mucus), especially during ovulating days. These changes are caused by rising levels of estrogen in the body needed to release an egg.

Ovulation calendars may not be perfect, but they may be fairly accurate. Additionally, the results may not be right if a woman is not sure about her last menstrual period or, or for women with irregular cycles. The calculators can give an idea about likely ovulation time. Combining the results while watching for the symptoms of ovulation may improve the accuracy of the calculation. These tools are based on averages, and even if women may be charting periods accurately, the cycle length and ovulation date may vary, cycle to cycle. These tools are most beneficial to women having regular periods by calculating the average cycle length and allowing them a wider fertility window to conceive.