Estimate your most fertile days and next ovulation date based on menstrual cycle length.
Result
Menstrual cycles fluctuate naturally. Not intended for contraception or medical diagnosis.
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Ovulation Day = Next Period Date - 14 Days | Fertile Window = Ovulation ± 5 Days
Last period: 01-Jan-2026 with 28-day cycle.
Ovulation Date: 15-Jan-2026 | Fertile Window: 10-Jan to 16-Jan.
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Open calculatorOvulation occurs approximately 14 days before the start of the next menstrual period (during the luteal phase), though individual cycles can fluctuate.
No. Biological cycles vary due to stress, illness, and hormonal changes. This tool is for fertility awareness only and should not be relied upon as a birth control method.
Because sperm can survive up to 5 days inside the female reproductive tract while an egg survives approximately 24 hours post-ovulation, the peak fertile window spans the 5 days leading up to ovulation and the day of ovulation itself.