Ovulation and fertile window calculator
Tap the first day of your last period and see your likely fertile days on a calendar, as a range, not one day. Free and private.
Tap the day your last period started
Not sure? Pick your best guess. You can change it any time.
November 2026
Common questions
Why does it show a range, not one day?
Ovulation does not fall on the same day of every cycle, and a calendar can only estimate it. So femio shows your likely fertile days as a range, never as one certain date.
Can I use it if my cycles are irregular or I have PCOS?
You can try it, and it will be honest with you. When your cycles vary too much it says “no confident fertile window this cycle” and explains how to tell afterwards whether you ovulated. With PCOS, ovulation test strips can read positive for much of the cycle, so use them with a second sign and talk to your clinician.
What signs can tell me ovulation is near?
Many women follow changes in cervical mucus, a positive ovulation test strip (a hormone surge, not proof that you ovulated) and their waking temperature, which confirms ovulation afterwards but cannot predict it. These signs work best alongside the calendar estimate.
These calculators give general estimates for learning and planning, not medical advice. Talk to your clinician about your health.