Menstrual Cycle Calculator
Estimate your next period date, fertile window, and ovulation day based on your last menstrual period and average cycle length.
Important Notes
What is a Menstrual Cycle?
A menstrual cycle is the monthly process the body goes through to prepare for a possible pregnancy. It is counted from the first day of one period to the first day of the next period.
How This Calculator Works
This calculator uses your last period date, average cycle length, and period length to estimate your next period, fertile window, and ovulation day. Ovulation usually happens around 14 days before the next period.
When to See a Doctor
Speak with a healthcare professional if your periods are very irregular, extremely painful, unusually heavy, absent for several months, or if you suspect pregnancy or a hormonal problem.
Medical Disclaimer
This calculator gives estimates only. Menstrual cycles can vary due to stress, health conditions, medication, breastfeeding, hormonal changes, or pregnancy. It should not be used as a medical diagnosis or as a reliable method of contraception.