Ovulation Calculator
Estimate your ovulation date and fertile window.
Ovulation dates are estimates and should not be used as the only method of contraception.
Ovulation calculator
Enter the first day of your last period and your average cycle details.
Cycle day 1 is the first day of menstrual bleeding.
Count from the first day of one period to the first day of the next.
Ovulation often occurs about 14 days before the next period.
Estimated ovulation date
Friday, July 31, 2026
Approximately cycle day 15, based on a 28-day cycle.
Estimated fertile window
Jul 26–Aug 1
About 5 days before ovulation through about 1 day after.
Next expected period
Aug 14
Luteal phase used
14 days
Ovulation and fertile window dates are estimates. This calculator does not diagnose fertility status, guarantee pregnancy chances, or replace professional reproductive health guidance.
Personalized interpretation
Based on your last period and cycle length, your estimated ovulation date is Friday, July 31, 2026.
Your estimated fertile window may be around Sunday, July 26, 2026 to Saturday, August 1, 2026.
Ovulation timing can shift from cycle to cycle, especially with stress, illness, travel, or irregular periods.
This calculator should not be used as the only method of contraception. If your cycles are very irregular or you have concerns, consider speaking with a qualified healthcare professional.
Fertile window timeline
Last period start
Jul 17
Fertile window start
Jul 26
Estimated ovulation
Jul 31
Fertile window end
Aug 1
Next expected period
Aug 14
Sperm can survive for several days, while the egg is viable for a shorter period after ovulation. Fertile window estimates are not exact.
How ovulation is estimated
Menstrual cycle phases explained
Menstrual phase
Cycle day 1 is the first day of menstrual bleeding.
Follicular phase
This phase can vary and affects when ovulation may occur.
Ovulation
An egg is released around the estimated ovulation date.
Luteal phase
The phase after ovulation is often more consistent but still varies.
Ovulation signs and tracking methods
Signs are not perfect, but combining methods may improve cycle awareness.
Irregular cycles and prediction limits
Predictions may be less reliable when cycles vary. Not everyone ovulates every cycle, and professional guidance may be useful for persistent irregularity.
Trying to conceive and when to seek advice
Timed intercourse around the fertile window may improve chances, but ovulation estimates are only one part of fertility.
Age, cycle regularity, health history, and partner factors can all matter. Individual circumstances vary.
Many guidelines suggest considering healthcare guidance if you have been trying for a long time, have very irregular cycles, or have reproductive health concerns.
Formula / date explanation
Next Expected Period = Last Period Start Date + Average Cycle LengthEstimated Ovulation Date = Next Expected Period − Luteal Phase LengthFertile Window ≈ 5 days before ovulation through about 1 day after ovulationA common default luteal phase is about 14 days. Average cycle length, luteal phase length, and ovulation timing can all vary.
Frequently Asked Questions
Related tools
More tools to try
Estimate only. This calculator is for general education and planning. It is not medical advice, and not medical, nutrition, fitness, diagnosis, treatment, or emergency advice. Personal factors can change results. Dates are estimates based on the inputs provided. Cycle length, ovulation timing, pregnancy dating, and medical factors can vary. Speak with a qualified professional for personal guidance.
Related reading
Learn the formula, assumptions, examples, or context behind this tool.