Ovulation Calculator
Estimate your ovulation date, fertile window, and next period from your last menstrual period and average cycle length.
Cycle details
Typical cycles range from 21 to 35 days. The average is 28.
Estimated ovulation date
June 03, 2026
Ovulating today
In fertile window
Fertile window
05/29/2026 to 06/04/2026
Next period
06/17/2026
Days to ovulation
0
Informational only, not contraception.
Frequently Asked Questions about the Ovulation Calculator
How does the ovulation calculator work?
It assumes a luteal phase of about 14 days, so ovulation lands at cycle length minus 14 days after your last period started. The fertile window covers 5 days before ovulation and 1 day after, based on sperm and egg lifespans.
How accurate is this estimate?
For women with regular 26 to 32 day cycles, the predicted window catches the true ovulation day in about 70% of cycles. Irregular cycles, stress, illness, and travel can shift ovulation. This is an estimate. Consult your doctor for fertility concerns.
What is a normal cycle length?
Cycles between 21 and 35 days are considered normal in healthy adults, with 28 days being the textbook average. Variation of a few days between cycles is normal. Persistently irregular cycles are worth discussing with a clinician.
When should I seek medical advice about my cycle?
Talk to a doctor if cycles are shorter than 21 days, longer than 35 days, vary by more than 7 to 9 days between cycles, or if you have been trying to conceive for over 12 months (or 6 months if you are over 35).
Is the fertile window the same as the ovulation day?
No. The egg lives 12 to 24 hours, but sperm can survive up to 5 days in fertile cervical mucus. That makes the 5 days before ovulation plus ovulation day itself the realistic window for conception.
Related Calculators
More calculators in "Health"