Fertility tool
Ovulation Calculator
Find your most fertile days for the next three cycles. Enter the first day of your last period and your average cycle length, and we will map your fertile window on a calendar.
Estimates assume ovulation about 14 days before your next period. Cycles vary, so ovulation tests or tracking your temperature give a more personal picture. This tool is not a form of birth control.
Common questions
What is the fertile window?
It is the six-day stretch ending on ovulation day. Sperm can survive up to five days, so sex in the days before ovulation gives the best chance of conceiving.
Can I use this if my cycles are irregular?
You can, but the estimate will be less reliable. Ovulation test strips or tracking basal body temperature can help pinpoint ovulation more accurately.
Is this a form of birth control?
No. This calculator is meant to help with conception and should not be used to prevent pregnancy.
