Track your menstrual cycle and calculate your fertile window
Percentages show the estimated chance of pregnancy for each day based on medical studies.
Input the first day of your last menstrual period. This is day 1 of your cycle.
Enter your average cycle length (typically 28 days, but can vary from 21-35 days). Track several cycles for accuracy.
Input how long your period typically lasts (usually 3-7 days).
Click calculate to see your estimated ovulation date and fertile window.
See a calendar view showing your period, fertile window, and estimated ovulation date.
Use the calculator regularly to track patterns and improve accuracy over time.
Use the information to plan for conception or identify days when extra contraception may be needed.
For conception planning or cycle concerns, consult with a healthcare provider for personalized guidance.
Calculators provide estimates based on averages. Actual ovulation can vary. For accuracy, combine with ovulation predictor kits or fertility tracking methods.
The fertile window is the 5-6 days before ovulation and the day of ovulation when conception is most likely. Sperm can survive up to 5 days in the reproductive tract.
Calendar-based methods are less reliable than other contraceptives. Consult healthcare providers for reliable birth control options.
Irregular cycles make prediction less accurate. Track multiple cycles, consider fertility tracking apps, or consult healthcare providers for guidance.
Track from day 1 of your period (first day of bleeding) to day 1 of your next period. Average several cycles for accuracy.
Yes, stress, illness, travel, and lifestyle changes can affect cycle timing and ovulation. The calculator provides estimates, not guarantees.
Common signs include increased cervical mucus, mild abdominal pain (mittelschmerz), slight temperature rise, and positive ovulation predictor kit results.
While less likely, pregnancy can occur outside the estimated fertile window. Sperm survival and cycle variations make exact prediction difficult.
Ovulation itself (egg release) happens quickly, but the egg is viable for 12-24 hours. The fertile window includes days before when sperm can survive.
Basal body temperature tracking can improve accuracy when combined with calendar methods. Temperature rises slightly after ovulation occurs.
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