Ovulation Calculator
Track your fertility window and find your most fertile days to increase chances of conception
This estimates ovulation as 14 days before the next period, using the cycle length you enter. The fertile window shown is the five days before that date through the day after. It is a calendar estimate, not a test.
Calculator Inputs
Usually 28 days
Results
Enter values above to see your results
Ovulation can shift even when cycles look regular. This is not medical advice and it cannot confirm or rule out pregnancy.
How It Works
Next period = first day of the last period + cycle length. Estimated ovulation = that next period minus 14 days. For a 28-day cycle that lands on day 14. For a 32-day cycle it lands on day 18.
The window opens five days before the estimated ovulation date, because sperm can survive for several days, and it closes the day after, because the egg is only viable for about a day. A positive ovulation test or a temperature shift is better evidence than this count.
Worked example
Period on 1 January 2026, 28-day cycle
1 Jan 2026 + 28 days= 29 Jan 202629 Jan 2026 - 14 days= 15 Jan 2026five days before ovulation through the day after= 10 Jan 2026 through 16 Jan 2026This is a calendar estimate. It does not confirm ovulation or pregnancy.
Tips & Best Practices
- •Sperm can survive for up to 5 days in the body, while an egg lives for only 12-24 hours.
- •The best time to conceive is the 2-3 days *before* ovulation.
- •Track other signs like basal body temperature and cervical mucus for better accuracy.
Frequently Asked Questions
Can I get pregnant outside my fertile window?
Pregnancy is much less likely once the egg is gone, about a day after ovulation. Cycle length can still be wrong, so a calculator cannot rule pregnancy in or out.
Guides & Articles
Due Date From Ovulation or Conception Date
Add 266 days to an ovulation date or a conception date. A worked example, why both dates use the same rule, and when the period method is the better start.
Ovulation Date vs Conception Date
Ovulation is the egg release. Conception is fertilization, usually within about a day. Implantation is later and is not the start of the 266-day due-date count.
How Is a Pregnancy Due Date Calculated?
280 days from the last menstrual period, or 266 days from ovulation. Naegele’s rule, a cycle-length adjustment, and three worked examples. The result is an estimate.
Related Calculators
Pregnancy Due Date Calculator
Estimate a due date from the first day of your last period
Due Date by Ovulation
Estimate a due date from an ovulation date or a conception date.
Pregnancy Week Calculator
See how many weeks and days pregnant you are from the first day of your last period.
Pregnancy Weeks to Months
Convert pregnancy weeks and days into a pregnancy month and a trimester.