Predict your ovulation day, fertile window, and next period based on your cycle details.
Predicted Ovulation Day:
14
Fertile Window:
9
Next Period Due Date:
1970-01-29
This calculator uses your last period date, average cycle length, and luteal phase length to estimate ovulation, the fertile window, and the next period date.
Key formula: ovulation_day = last_period_start_date + (average_cycle_length - luteal_phase_length)
ovulation_day = last_period_start_date + (average_cycle_length - luteal_phase_length)
Example inputs: last period start = 2025-07-01, average cycle = 30 days, luteal phase = 14 days.
These are estimates based on average cycle values. Individual variation is common, so use results as a guide rather than a definitive medical prediction.
If cycle length varies significantly, predictions are less reliable. Track multiple cycles or use ovulation tests for better timing and consult a healthcare provider if irregularities persist.
Conception is less likely outside the fertile window but possible; sperm can survive up to five days and ovulation timing can vary, so occasional conception outside the window can occur.
Yes. LH ovulation tests and tracking basal body temperature or cervical mucus can provide more precise timing and complement the calculator's estimates.
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