Ovulation Calculator
Calculate your fertile window and ovulation dates based on your menstrual cycle
Ovulation Calculator
The Ovulation Calculator estimates the most probable ovulation/fertile window as well as other related dates. The estimations are based on a woman's last period date. This calculator should not be used as a form of birth control.
đ Period Details
đ Ovulation Results
August 2025
đ Important dates for the next 6 cycles
| Period Start | Ovulation Window | Due Date |
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đ Understanding Ovulation
Ovulation and Conception
Ovulation in humans is the process by which ovarian follicles rupture and release one or more mature eggs from the ovaries. On average, ovulation occurs within the 4 days before or after the midpoint of a woman's menstrual cycle (14 days before the start of a woman's next menstrual period).
Day 10-18 of the menstrual cycle (on average) is the most fertile phase of the menstrual cycle. This is important when trying to conceive because fertilization of the egg can only occur for 12-24 hours after release during part of the luteal phase.
Tracking Menstrual Cycles
This ovulation calculator uses the method of tracking menstrual cycles in order to predict when ovulation occurs. Since day 10-18 of the menstrual cycle is typically the most fertile phase, women with regular cycles can fairly easily determine when they are ovulating.
The first day of the menstrual cycle is the day that bleeding starts, and it ends the day that bleeding starts again. It can be helpful to maintain a menstrual calendar to determine how regular your periods are.
Tracking Basal Body Temperatures
Basal body temperature (BBT) is measured using a special thermometer. This is your temperature when you first wake up in the morning. BBT is generally at the lowest level right before ovulation occurs. It starts rising by about ÂŊ a degree a day during ovulation. Tracking BBT over a few months can help you determine when you are ovulating.
Ovulation Kits
It is also possible to use an over-the-counter ovulation test that tests for a surge in specific hormones that precede ovulation by 24-48 hours. While these tests are 99% accurate in detecting the specific hormones, they cannot guarantee when exactly ovulation will occur within the two-day period. These tests typically measure the level of luteinizing hormone (LH).