Calculator
Ovulation Calculator
First day of last period
28 days
ℹ️ Medical disclaimer: This tool provides estimates only and is not a contraceptive method. Consult a healthcare provider for medical advice.
28 days
20283545
5 days
1510
Fertile window
June 2026
Sun
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Sat
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Period
Fertile
Ovulation
Today
Ovulation in 14 day(s)
Fertile window starts in 9 day(s)
PeriodJun 21, 2026 – Jun 25, 2026
Fertile windowJun 30, 2026 – Jul 6, 2026
OvulationJul 5, 2026
Next periodJul 19, 2026
Next 3 cycles
Cycle 1
🥚 Jul 5, 2026Period: Jul 19, 2026
Cycle 2
🥚 Aug 2, 2026Period: Aug 16, 2026
Cycle 3
🥚 Aug 30, 2026Period: Sep 13, 2026
Optional signals
Low fertility
Formula: Ovulation = Last Period + (Cycle Length − 14 days) · Fertile Window = Ovulation − 5 to +1 days
Frequently Asked Questions
How does the ovulation calculator work?
It estimates the fertile window based on your last menstrual period (LMP) and typical cycle length. Ovulation usually occurs around day 14 of a 28-day cycle, but this varies. The fertile window spans roughly 5 days before ovulation plus the day of ovulation itself.
How accurate is ovulation prediction based on cycle length?
Cycle-based calculation is an estimate. Actual ovulation can shift due to stress, illness, weight changes, or hormone fluctuations. For higher accuracy, combine with basal body temperature (BBT) tracking or LH surge tests.
Can I use this to prevent pregnancy?
No. Calendar-based methods have high failure rates as a contraceptive. Consult a healthcare provider for reliable contraception options. This tool is intended to help those trying to conceive, not prevent pregnancy.