Ovulation Calculator
Estimate your likely ovulation date, fertile window and next period from the first day of your last period, cycle length, period length and luteal phase.
Results are calendar estimates based on cycles from 21-40 days, periods from 2-10 days and luteal phases from 10-16 days. This is not a diagnosis or a contraception plan.
How the fertile window is estimated
Ovulation calculator results in US search are expected to show a likely ovulation date and the fertile window. The estimate works best for people with fairly regular cycles.
A common calendar estimate uses a luteal phase near 14 days.
The highest-chance window commonly includes the five days before ovulation plus ovulation day.
Ways to confirm ovulation
- LH ovulation predictor kits can help identify a hormone surge before ovulation.
- Basal body temperature can confirm ovulation after it has happened.
- Cervical mucus changes can add context but are subjective.
- A clinician can help if cycles are irregular, painful or fertility concerns persist.
Frequently Asked Questions
Sources and References
- Trying to Get Pregnant? Here's When to Have SexACOG
- Fertility Awareness-Based Methods of Family PlanningACOG
- Ovulation Calendar and CalculatorCleveland Clinic
- Timing of sexual intercourse in relation to ovulationNew England Journal of Medicine / PubMed
Calculations are based on the listed reference sources. Links open in a new tab.
Related Tools
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