Tools
Ovulation calculator
Estimate your ovulation day and fertile window from your last period start and typical cycle length. This is calendar math using a common luteal-phase average — a sketch, not a sensor.
Your estimate
- Estimated ovulation
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- Estimated fertile window
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- Most fertile days
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- Estimated next period
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Based on a 14-day luteal-phase average. Your ovulation day can shift from cycle to cycle.
How this estimate works
The calculator adds your cycle length to the first day of your last period to sketch the next period, then counts back about 14 days for a typical luteal phase. The fertile window is drawn as the five days before that ovulation estimate plus the day itself. That pattern matches common calendar tools — and the same limits: irregular cycles, short or long luteal phases, and cycle-to-cycle shifts mean the dates can be wrong for you.
Body signs such as basal temperature, cervical mucus, and ovulation tests give a clearer picture than the calendar alone. Lua’s Trying to conceive mode keeps those logs next to your cycle, on your phone.
These tools give calendar estimates based on averages. They are not medical advice, not a fertility diagnosis, and not a method of contraception. Cycles vary. If you are trying to conceive or have concerns about your cycle, talk with your clinician.
One app for your cycle, contraception, fertility and pregnancy.
Private, flexible and designed to adapt with you.