Estimate the 'safer' and fertile days of your menstrual cycle based on the rhythm method for fertility awareness.
"Safe days" refer to the time in a woman's menstrual cycle when the chances of getting pregnant are at their lowest. This calculation is based on the **rhythm method**, a form of fertility awareness that tracks the cycle to predict fertile and infertile phases.
The rhythm method is **not a reliable form of contraception**. Ovulation can be affected by stress, illness, and other factors, making predictions inaccurate. For effective birth control, please consult a healthcare provider.
Maintained by Live Fitness Check. Last updated: September 1, 2026. How we test our calculators .
Estimates lower- and higher-fertility days from menstrual-cycle dates and average cycle length.
The calculator estimates the likely ovulation period from cycle timing and marks surrounding days according to its configured fertility-window rules. The calculation uses last menstrual period date and average cycle length.
Calendar estimates cannot reliably guarantee contraception because ovulation can vary even in usually regular cycles. Use the number as an estimate and consider professional advice when the result may affect health, treatment, pregnancy, nutrition, exercise safety or another important decision.
