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Ovulation Calculator
Calculate your ovulation date and fertile window based on your cycle length.
How it works
This calculator uses the calendar method: ovulation occurs approximately 14 days before your next period. For a 28-day cycle, that is day 14; for a 32-day cycle, day 18. The fertile window spans 5 days before ovulation, ovulation day, and 1 day after.
Frequently Asked Questions
When does ovulation occur?+
About 14 days before the next period. In a 28-day cycle, day 14; in a 32-day cycle, day 18. Source: ACOG.
What is the fertile window?+
The 5 days before ovulation plus the day of ovulation itself. Sperm survive up to 5 days in the uterus; the egg lives 12–24 hours after release.
How accurate is the calendar method?+
Reasonably reliable for regular cycles (±2 days). For irregular cycles, LH ovulation tests or basal body temperature tracking are more accurate.
What are signs of ovulation?+
Clear, stretchy cervical mucus (egg-white texture), slight rise in basal body temperature (0.2–0.5 °C), mid-cycle pelvic pain, and increased libido.
Can this calculator be used for contraception?+
No. The calendar method has a Pearl index of 9–40 and is not adequate as a sole contraceptive. Symptothermal (FAM) methods are safer.
When is conception most likely?+
Highest 1–2 days before ovulation (~33 % per cycle per Wilcox 1995). Intercourse every 1–2 days during the fertile window maximizes the chance.
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Background
Calculate Ovulation: How to Determine Your Fertile Days
7 min