Ovulation Calculator

Ovulation Calculator is a clean, fast way to estimate your most fertile days, your ovulation date, your next period and an estimated due date — all from one simple input: the first day of your last menstrual period. Everything is calculated on your device, completely offline.

WHAT YOU CAN DO
• Enter the first day of your last period and your average cycle length (20–45 days)
• See your estimated ovulation day at a glance
• View your fertile window — the six days when conception is most likely
• Get your estimated next period date
• See an estimated due date if conception occurs (Naegele's rule)
• Look ahead at the fertile windows for your next three cycles

HOW IT WORKS
The calculator uses your cycle length and a typical 14-day luteal phase. Ovulation is estimated as roughly 14 days before your next expected period, and the fertile window covers the five days before ovulation plus the day of ovulation itself, since sperm can survive several days. The estimated due date is 280 days (40 weeks) from the first day of your last period.

PLAN OR UNDERSTAND YOUR CYCLE
Whether you are trying to conceive, spacing pregnancies, or simply want to understand your body better, the Learn tab explains the menstrual cycle, ovulation and the fertile window in plain language.

IMPORTANT: AN ESTIMATE, NOT MEDICAL ADVICE
These results are estimates based on averages and a regular cycle. They are not a substitute for professional medical advice, diagnosis or treatment, and they are NOT a form of contraception or birth control. Cycles vary from person to person and month to month. Do not rely on this app to prevent pregnancy. For medical or family-planning decisions, consult a qualified healthcare provider.

PRIVACY
The app collects no personal data and works fully offline — the dates you enter never leave your device. Ads are served by Google AdMob, which may use an advertising identifier as described in Google's policies.

Light and dark themes, a tiny download, and no clutter. Download Ovulation Calculator and understand your cycle with confidence.