Ovulation & Fertile Window Calculator
Enter the first day of your last period and your usual cycle length, and we will estimate your fertile window and most likely day of ovulation. This is an estimate to help you plan, not a certainty.
Your estimated fertile window
Educational, not medical advice. This calculator uses the standard method (ovulation about 14 days before your next period, with a fertile window of roughly six days). Cycles vary, so treat this as a guide. It runs in your browser and stores nothing.
When to see a doctor
If you are under 35 and have been trying for a year, or over 35 and trying for six months, it is worth seeing a doctor. Also see one for very irregular or missing periods, severe period pain, or any bleeding that worries you. A calculator cannot diagnose fertility.
Go further
The Trying-to-Conceive Blueprint
A private community for women trying to conceive, honest guidance, and a professional to ask.
See the program →