Free online ovulation tracker. Enter your last period date and cycle length to calculate ovulation day, fertile window, and safe days. Helps women identify the best time to conceive. | No registration · Data never leaves your device
Zero dependencies · Works offlineEnter your last period and cycle length to calculate ovulation and fertile window
1. Enter the first day of your last period.
2. Enter your cycle length (days from day 1 of period to day before next period, typically 28 days).
3. Enter period length (how many days bleeding lasts, typically 3-7 days).
4. Click "Calculate" to see your ovulation day, fertile window, and next period date.
Ovulation typically occurs 14 days before your next period. So: Ovulation Day = Last Period + Cycle Length - 14. For a 28-day cycle, ovulation is on day 14.
Sperm can survive 3-5 days in the body, and the egg lives about 24 hours. The fertile window spans 5 days before to 1 day after ovulation — about 6-7 days total. This is the best time for conception.
This tool is based on a standard cycle model and works best for women with regular cycles. Actual ovulation can shift due to stress, illness, etc. For irregular cycles, use ovulation test kits or consult a doctor.
The rhythm method has a high failure rate (~24%) and is not recommended as a sole contraceptive. This tool is for reference only — do not rely on it as your only birth control method.