Enter your last period date and cycle length to find your ovulation day, fertile window, and the best days to conceive.
The date your most recent period started
Count from first day of one period to first day of next. Average is 28 days.
Time between ovulation and next period. Usually 14 days — leave as is if unsure.
Ovulation Day
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🟢 Fertile window starts--
🔴 Most fertile days--
🟢 Fertile window ends--
📅 Next period expected--
🧪 Best days for pregnancy test--
Your Cycle at a Glance
PeriodFertile windowOvulation day
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How to Use the Ovulation Calculator
To get the most accurate results, enter the first day of your last menstrual period (LMP) and your average cycle length. Your cycle length is the number of days from the first day of one period to the first day of the next. The average is 28 days, but anywhere from 21 to 35 days is considered normal.
When Does Ovulation Occur?
Ovulation typically occurs 14 days before your next expected period. This is calculated by subtracting your luteal phase length (usually 14 days) from your total cycle length. For a 28-day cycle, ovulation happens around day 14. For a 32-day cycle, it happens around day 18.
The Fertile Window Explained
Your fertile window spans 6 days — the five days before ovulation and the day of ovulation itself. This is because sperm can survive in the reproductive tract for up to 5 days, while the egg is only viable for 12–24 hours after release. The two most fertile days are the day before and the day of ovulation.
Signs of Ovulation
Common signs include a change in cervical mucus (becomes clear and stretchy like egg whites), a slight rise in basal body temperature (BBT), mild one-sided pelvic pain (mittelschmerz), and a positive ovulation predictor kit (OPK) result. Tracking these signs alongside this calculator gives you the most accurate picture of your fertile days.
Frequently Asked Questions
Ovulation typically occurs about 14 days before your next period. For a 28-day cycle, this is usually around day 14. This calculator estimates your ovulation day based on your cycle length and luteal phase.
The fertile window is the 6-day period ending on the day of ovulation. Sperm can survive up to 5 days, so you can conceive from intercourse during these days. The most fertile days are the day before and day of ovulation.
This calculator is an estimate based on average cycle patterns. It is most accurate for women with regular cycles. Stress, illness, or hormonal changes can shift ovulation. Use ovulation predictor kits (OPKs) for greater accuracy.
A normal menstrual cycle ranges from 21 to 35 days, with 28 days being the average. It is counted from the first day of one period to the first day of the next.
It is very unlikely. The egg is only viable for 12–24 hours after ovulation. However, because sperm can live up to 5 days, the days just before ovulation carry the highest conception risk.