Menstrual Cycle &
Ovulation Calculator
Explore estimates for your next period, ovulation and possible fertile window.
Calculate your cycle
Choose the option that works for you.
Your estimated results
Calculation assumptions: next period = latest start + cycle length; ovulation = 14 days before that estimated date; possible fertile window = 5 days before through 1 day after estimated ovulation. This fixed rule is only an educational approximation. Actual ovulation can differ and the window does not identify every day pregnancy is possible. Stress, illness, hormonal medication, breastfeeding and irregular cycles can affect timing.
Your cycle summary
One-cycle calendar
* Other days are not confirmed safe for avoiding pregnancy. The final highlighted date is the estimated start of the next period, not an additional cycle. All dates are estimates.
What are “safe days”?
Some fertility-awareness approaches describe days outside an estimated fertile window as lower-fertility days. However, a calendar cannot confirm which days are safe from pregnancy. Ovulation can shift even with regular cycles, and pregnancy may still occur outside the predicted window.
Standard Days Method: For cycles usually 26–32 days, this method considers days 8–19 potentially fertile. It is a separate fertility-awareness method, not a result of this calculator's four-date average. This calculator does not provide contraception instructions or identify pregnancy-free dates.
For pregnancy prevention or personal medical questions, speak with a qualified healthcare professional. CDC: Standard Days Method · NHS: Fertility awareness