Default luteal phase is 14 days. Fertile window is modeled as 5 days before ovulation through 1 day after. Next period = LMP + cycle length. Not for contraception.
Cycle day 1 anchors all estimates.
Customize if you track temperature or apps with known luteal length.
See the window, next period, and current cycle day.
Luteal phase 14 days.
Ovulation ≈ June 15; next period ≈ June 29.
Assuming every cycle is 28 days
Fix: Enter your average cycle length.
Using estimates as contraception
Fix: Use medically approved birth control methods.
Estimate your ovulation day and fertile window from cycle length, period start, and luteal phase.
Typical 21–45; default 28
Usually 10–18; default 14
Optional for calendar context; 2–10
Result
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Enter your last period date and cycle length, then click Calculate.