Period Calculator
Ovulation, fertile window & next period
About this tool
Period Calculator estimates your next period date, ovulation day, and fertile window based on your last period start date and cycle length. It also provides a 3-month forecast. Use it as a reference for pregnancy planning or health tracking — it does not replace medical advice.
How to use
- Select the start date of your last period.
- Adjust your cycle length and period length.
- Your next period, ovulation day, fertile window, and 3-month predictions are shown.
FAQ
How is the ovulation day calculated?
It is estimated by subtracting 14 days from your next expected period date. For a 28-day cycle, ovulation typically occurs on day 14.
What is the fertile window?
The fertile window is the days around ovulation when pregnancy is most likely — generally from 5 days before ovulation to 1 day after.
Can I use this as a contraceptive method?
No. This tool is for reference only. Menstrual cycles can vary due to stress, health conditions, and other factors. Consult a healthcare professional for reliable guidance.
Results are for reference only. Please verify with official sources