Ovulation Calculator
By Miikka · CalcBrew · Updated
The Ovulation Calculator estimates when ovulation, the release of an egg, happens and which days make up your fertile window, based on your menstrual cycle. It helps you see when the chance of conceiving is at its highest.
How the calculator works and what it’s for▾
How the calculator works
The calculator estimates the timing of ovulation from the length of your cycle and the start date of your last period. Around that point it maps a fertile window when conception is most likely.
Because the estimate relies on cycle regularity, the steadier your cycle, the more accurately the timing can be predicted.
What you enter and what you get
You enter the start date of your last period and your typical cycle length. The calculator shows the estimated ovulation day and the fertile window around it.
The result helps you time intercourse for the days when the chance of pregnancy is greatest.
Who it is for
The calculator serves those hoping to conceive who want to time attempts to their fertile window. It can also be used simply to track and understand your own cycle.
It is especially suited to cases where the cycle is fairly regular and its length is known.
Good to know
The results are estimates and do not replace ovulation tests or medical advice. Individual variation and an irregular cycle affect accuracy.
Use the calculator as a planning aid, and where needed also draw on other body signals and guidance from healthcare professionals.
🔄 Reviewed June 2026
Frequently asked questions
Cite this calculator
CalcBrew. (2026). Ovulation Calculator. https://calcbrew.com/ovulation-calculator“Ovulation Calculator.” CalcBrew, 2026, calcbrew.com/ovulation-calculator.Link to https://calcbrew.com/ovulation-calculator. Results are estimates; cite the underlying formula or data source for academic work.
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