Free tool
Ovulation calculator
See your next estimated fertile windows, ovulation days and periods.
Estimates for planning, not birth control. Talk with your provider.
Your windows will appear here
Add the first day of your last period to see estimated fertile windows. Already pregnant? Try the due date calculator.
Questions
About this calculator
How are the fertile windows estimated?
Ovulation is estimated 14 days before your next expected period. The window shown runs from 5 days before that day to 1 day after.
Can I use this to avoid pregnancy?
No. These are calendar estimates for planning, not birth control. Please talk with your provider about contraception.
Can SwyftMom track this for me?
Yes. The free plan includes cycle tracking and a fertile window estimate. Premium adds LH and BBT logging with monthly fertility reports.
Track your cycle with SwyftMom.
Cycle, fertile window, LH and BBT, all in one place.