Ovulation Calculator
Calculate your fertile window and ovulation date. Track your menstrual cycle and plan accordingly.
Your Ovulation & Fertility Details
How to use the Ovulation Calculator
- Enter the first day of your last period.
- Enter your average cycle length (usually 21–35 days).
- Click Calculate to see your estimated ovulation day and fertile window.
- Track a few cycles to see how regular your dates are.
Formula used
The fertile window is roughly the 5 days before ovulation plus the day of ovulation, because sperm can survive up to 5 days.
Worked example
Period started 1 January 2026, 28-day cycle
Next period expected 29 January
Ovulation likely around 15 January
Fertile window about 10–15 January
Tips for accurate results
- Cycle length can vary month to month; use an average of 3–6 cycles.
- Ovulation test kits (LH strips) and basal body temperature can confirm the timing.
- This calculator is not a reliable method of contraception.
Frequently Asked Questions
It is unlikely but possible, especially with irregular cycles.
Calendar estimates become less reliable; ovulation kits or consulting a doctor help.
The egg lives about 12–24 hours after release.
Content reviewed by Vinod, Easy Smart Calculator · Last updated October 2026
Understanding Your Cycle
Menstruation: First 5 days. Uterine lining sheds. Fertility is low but possible.
Fertile Window: 5 days before ovulation + day of ovulation. Best time to conceive.
Ovulation: Around day 14 of a 28-day cycle. Egg is released and viable for 12-24 hours.
Luteal Phase: After ovulation. Fertility decreases. Next period expected ~14 days after ovulation.
Key Facts
- Sperm can survive 3-5 days in reproductive tract
- Egg is viable for 12-24 hours after ovulation
- Cycle varies person to person (21-35 days normal)
- This is an estimate. Consult your doctor for medical advice