Utilz
Ovulation Calculator
Find your fertile window and ovulation day
days
Why Use This Tool?
- Identify your most fertile days to maximize chances of conception.
- Visual calendar makes it easy to see fertile and period days at a glance.
- Private and simple — no account needed, all calculations in your browser.
Formula
Ovulation typically occurs 14 days before the next period. Ovulation Day = LMP + (Cycle Length - 14). The fertile window spans 5 days before ovulation through 1 day after.
How to Use
- Enter the first day of your last period
- Enter your cycle length (default 28 days)
- View your ovulation day, fertile window, and next period
- Check the visual calendar for key dates
FAQ
How accurate is an ovulation calculator?
It provides an estimate based on average cycle patterns. Actual ovulation can vary by a few days. For more precision, combine with ovulation test kits or basal body temperature tracking.
What is the fertile window?
The fertile window is the 6-day period ending the day after ovulation. Sperm can survive up to 5 days, so conception is possible from 5 days before to 1 day after ovulation.
Can I use this to prevent pregnancy?
This calculator is intended for conception planning. It should NOT be relied upon as a contraception method, as ovulation timing can vary unpredictably.