🌺 Fertility

Ovulation Calculator

Enter the first day of your last period and your average cycle length to find your most fertile days and estimated ovulation date.

First day of last period

Average cycle length (days)

Ovulation Day
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Peak Fertile Day

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Day before ovulation

Fertile Window Opens

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5 days before ovulation

Next Period Due

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Your Cycle at a Glance

Non-fertile

Fertile window

Peak day

💡 The fertile window is typically 5 days before ovulation plus the day of ovulation itself. The two most fertile days are the day before and the day of ovulation. Cycle lengths vary — track a few cycles for the most accurate picture.

Frequently Asked Questions

How is my ovulation date calculated?

Ovulation typically occurs 14 days before your next period, not 14 days after your LMP. So for a 28-day cycle it's day 14, but for a 32-day cycle it's day 18. This calculator subtracts 14 from your cycle length and adds that to your LMP date.

What is the fertile window?

Sperm can survive in the reproductive tract for up to 5 days, so having sex in the 5 days before ovulation — plus the day of ovulation itself — gives you the best chance of conception. The day before ovulation is typically the most fertile day.

How do I know my cycle length?

Count from the first day of one period to the first day of the next. The average is 28 days, but anywhere from 21–35 days is considered normal. Tracking 2–3 cycles gives you a reliable average.

Can my ovulation date change?

Yes. Stress, illness, travel, and hormonal changes can all shift ovulation. This calculator gives an estimate based on a regular cycle — for the most accurate ovulation tracking, consider using ovulation predictor kits (OPKs) or basal body temperature (BBT) charting.

Is this medical advice?

No — this tool is for informational purposes only. Always follow the guidance of your doctor or midwife for fertility and conception questions.