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health calculator
Estimate conception date and fertile window.
Save this page to track cycle updates and fertility planning windows.
Estimated ovulation day
Day 14
Summary
Ovulation day
Day 14
Estimated release day.
Fertile start
Day 9
Conception window begins.
Fertile end
Day 15
Conception window closes.
Cycle length
28 days
Menstrual interval.
D3 visualization
Visualize the relative duration of your peak fertile days in a full cycle.
D3 visualization
Track critical cycle day boundaries including estimated ovulation and fertility window.
Guide
Conception planning estimates the fertile window around the day of ovulation. In a typical menstrual cycle, ovulation occurs roughly 14 days before the next period starts. The fertile window represents the days preceding ovulation and the ovulation day itself, when conception is biologically possible.
Ovulation
The release of a mature egg from the ovary, making fertilization possible.
Luteal phase
The post-ovulation phase of the cycle, typically lasting 10 to 16 days.
Conception is most likely during the fertile window, particularly in the 2 days leading up to and including ovulation.
Formula
Ovulation day = cycle length - luteal phase lengthThe fertile window is estimated around ovulation. Actual ovulation can vary cycle to cycle.
Step by step
Example
With a 28-day cycle and 14-day luteal phase, estimated ovulation is around day 14 and the fertile window starts around day 9.
Related guides
Guide
Understand conception timing, how sperm and egg viability affect fertility windows, and how to use ovulation tracking for planning or preventing pregnancy.
Guide
Track your ovulation cycle with calendar methods, basal body temperature, cervical mucus, and ovulation predictor kits to identify your most fertile days.