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Calculators/Pregnancy
Ovulation Calculator
Calculate your estimated ovulation date and fertile window based on your last period and average cycle length. Ideal for natural family planning and conception timing.
28 days
Fertile Window
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OV
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OvulationFertile
Ovulation Date
Jul 7, 2026
Fertile Window
Jul 2, 2026 – Jul 8, 2026
Next Period
Jul 21, 2026
How to Use This Calculator
1
Enter your last period date
Enter the first day of your most recent menstrual period — the day bleeding started, not spotting. This is Day 1 of your cycle. The calculator uses this to estimate when ovulation occurs in your current or upcoming cycle.
2
Set your average cycle length
A typical cycle is 21–35 days, with 28 days being average. Count from the first day of one period to the first day of the next. If your cycles vary, use your average. Cycles shorter than 21 or longer than 35 days may indicate irregular ovulation.
3
Fertile window explanation
Ovulation typically occurs 14 days before your next period (not 14 days after LMP). The egg survives 12–24 hours after ovulation. Sperm survive 3–5 days in the reproductive tract. Combined, this creates a fertile window of 5–6 days: 5 days before ovulation through 1 day after.
Real-World Examples
28-Day Cycle
Last Period
June 1
Cycle Length
28 days
ResultOvulation: June 15
Fertile window: June 10–16. Next period: June 29.
32-Day Cycle
Last Period
June 1
Cycle Length
32 days
ResultOvulation: June 19
Longer cycles shift ovulation later but the luteal phase (14 days) stays consistent.
Frequently Asked Questions
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