Period Calculator & Cycle Tracker
Predict your next period, ovulation, and fertile window. Enter the first day of your last period and your typical cycle information to get started.
Your Next Cycle Prediction
Enter your details above to forecast your upcoming cycle.
Understanding Your Menstrual Cycle
Your menstrual cycle is much more than just your period. It's a complex monthly process your body undergoes to prepare for a potential pregnancy. A cycle is counted from the first day of one period to the first day of the next. Understanding this rhythm can help you recognize what's normal for your body and identify your most fertile days.
How This Period Calculator Works
This tool uses your last menstrual period (LMP) and cycle length to predict future dates. A key concept in this calculation is the **luteal phase**—the time from ovulation to your next period—which is consistently about 14 days long for most women. The calculator:
- Determines the start of your next period by adding your cycle length to your last period's start date.
- Identifies your likely ovulation day by subtracting 14 days from your next period date.
- Calculates your fertile window, which includes the five days before ovulation and ovulation day itself. For a more detailed look at this time, you can use our dedicated Ovulation Calculator.
What Is a "Normal" Cycle?
There is a wide range of what's considered "normal." An adult's cycle can last anywhere from 21 to 35 days, and a period can last from 2 to 7 days. It's also normal for your cycle length to vary by a few days each month. Factors like stress, diet, significant changes in exercise, and medical conditions can all affect your cycle's regularity.
Tracking your cycle is a powerful way to understand your body's patterns. If you are trying to conceive, knowing your cycle is the first step. You can use our Conception Calculator to help estimate when you became pregnant.
If your period is late and you think you may be pregnant, you can get a glimpse of your potential timeline with our Due Date Calculator.
Disclaimer: This calculator provides an estimation and should be used as a guide, not a medical tool. The predictions are most accurate for women with regular cycles. If you have concerns about your cycle, please consult a healthcare professional.