Ovulation & Fertility Calculator
Predict your most fertile window using your last period and cycle length.
Your Cycle Details
This is the first day of your last period.
Estimated Ovulation Date
—
Day when you are most likely to ovulate.
Peak Fertility Window
—
Best days for conception (if attempting).
How the Ovulation Window is Determined
The **Ovulation Calculator** predicts your fertility window by relying on the fact that the time between **ovulation** and the start of the next period (**Luteal Phase**) is highly consistent, typically lasting **14 days**.
Calculation Method
The method determines the key dates as follows:
- **Ovulation Date:** $\text{Start of next period} – 14 \text{ days}$ (Since the next period is your LMP + Cycle Length).
- **Fertility Window:** The 6 days leading up to and including the predicted ovulation date.
Key Terms (FAQ)
What is the “Fertility Window”?
The fertility window is a six-day period during the menstrual cycle—the five days before ovulation and the day of ovulation itself—when unprotected intercourse can result in pregnancy.
How accurate is an online ovulation calculator?
Online calculators provide a reliable estimate for women with **regular cycles**. If your cycle is irregular, these estimates may be less accurate, and methods like basal body temperature (BBT) monitoring or ovulation predictor kits (OPKs) are recommended for greater precision.