Predict your upcoming period dates and estimated fertile window based on your last period and average cycle length.
This tool estimates the start date of your next menstrual period and fertile window based on your average cycle length and the start date of your last period. It's used for general menstrual cycle tracking and family planning awareness, not as a medical diagnostic tool.
The calculator adds your average cycle length (commonly 28 days, though this varies by individual) to the start date of your last period to estimate the next period's start date. Ovulation is typically estimated to occur around 14 days before the next expected period.
Enter the start date of your last period and your typical cycle length, and the calculator estimates your next period date and fertile window.
Example: If your last period started on the 1st and your average cycle is 28 days, your next period is estimated to start around the 29th.
How accurate is this prediction? It provides a general estimate based on average cycle length. Actual cycles vary due to stress, illness, travel, and other factors, so treat this as an approximation rather than a guarantee.
What is considered a normal cycle length? Cycle lengths between 21 and 35 days are generally considered typical for adults, though what's "normal" varies significantly between individuals.
Should I track my cycle over several months for better accuracy? Yes, tracking multiple cycles helps identify your personal average and any variability, which improves the accuracy of future predictions.
Can irregular cycles affect this calculator's accuracy? Yes, if your cycles vary significantly month to month, predictions based on a single average length will be less reliable than for someone with a very regular cycle.
Should I consult a doctor about irregular periods? If your cycles are consistently irregular or you have concerns about your menstrual health, it's advisable to speak with a healthcare provider rather than relying solely on this tool.