Ovulation Calculator
Find your fertile window, predicted ovulation date, and best days to try to conceive — based on your last period and average cycle length.
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Ovulation
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Fertile Window
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OPK Start
Your Cycle Information
💡 Most women have a luteal phase of 12-16 days (default: 14). Your cycle length can vary month to month — enter your actual average for a more accurate estimate.
Your Cycle at a Glance
Oct 3, 2026
Ovulation Date
Sep 28 – Oct 4, 2026
Fertile Window
Oct 17, 2026
Next Period
Sep 29, 2026
OPK Test Start
Fertile Window & Best Days to Try
Your 6-day fertile window runs Sep 28 – Oct 4, 2026. The days with the highest odds are the 3 days ending on ovulation day.
Oct 1
2 days before
Oct 2
1 day before
Oct 3
Ovulation Day
Next 3 Predicted Ovulation Dates
Assuming your 28-day cycle stays consistent going forward.
This Cycle
Oct 3, 2026
Cycle +1
Oct 31, 2026
Cycle +2
Nov 28, 2026
Understanding Your Fertile Window
Ovulation is the release of a mature egg from the ovary, and it’s the single most important event for trying to conceive (TTC). The egg itself is only fertilizable for roughly 12-24 hours, but sperm can survive inside fertile cervical mucus for up to 5 days waiting for it — which is why your realistic fertile window is 6 days long: the 5 days before ovulation plus ovulation day itself, not just one moment. This calculator estimates that window from your last period and your typical cycle rhythm; it doesn’t try to pinpoint one exact conception date or a due date — for that, see our conception calculator.
How These Dates Are Calculated
Ovulation Date = Last Period Start + (Cycle Length − Luteal Phase) daysFertile Window = Ovulation Date − 5 days through Ovulation Date + 1 dayBest Conception Days = the 3 days ending on Ovulation DateOPK Test Start = Ovulation Date − 4 daysNext Period = Last Period Start + Cycle Length daysWhy the luteal phase matters: for most people the luteal phase (ovulation to next period) is fairly fixed at 12-16 days, while the days leading up to ovulation can shift with stress, illness, or travel. That means your ovulation date can move around within a cycle even when your cycle length stays the same — using your actual luteal phase, not a flat “day 14” assumption, gives a more accurate estimate.
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Track BBT
Take your basal body temperature every morning before getting up. A sustained 0.2-0.5°F rise confirms ovulation already happened — useful for spotting your pattern, not for predicting it in advance.
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Use OPK Strips
Ovulation predictor kits detect the LH surge that triggers ovulation 24-36 hours later. Start testing a few days before your predicted fertile window opens and test at the same time each day.
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Cervical Mucus Signs
As estrogen rises, mucus shifts from dry or sticky to a clear, stretchy, egg-white texture. That egg-white stage is your most fertile sign and usually lines up with the days right before ovulation.
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Time Intercourse
Because sperm can survive up to five days but the egg is only viable for 12-24 hours, having intercourse every 1-2 days across the fertile window covers your bases better than aiming for one exact day.
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