About the Ovulation Calculator
This estimates your ovulation day and fertile window, assuming ovulation about 14 days before your next period. Cycles vary month to month, so it's approximate — and not a reliable form of birth control.
How it’s calculated
Ovulation ≈ next period − 14 days. Fertile window ≈ 5 days before to 1 day after ovulation.
Example calculation
A last period on January 1 with a 28-day cycle puts estimated ovulation around January 15.
Frequently asked questions
Can I use this to avoid pregnancy?
No — it isn't reliable for contraception. Cycles and ovulation timing vary, so the fertile window is only approximate. Speak to a healthcare provider about birth control.
What if my cycles are irregular?
The estimate is least reliable with irregular cycles. Ovulation predictor kits or a provider's guidance are more dependable in that case.
This tool provides a general, informational estimate only. It is not medical advice and cannot diagnose, treat, or replace guidance from a qualified healthcare professional. Individual health depends on many factors this estimate does not capture. If you have questions about your health, talk to a doctor.