Ovulation Calculator

Understand your ovulation and fertile window

Why ovulation timing varies

Ovulation is influenced by cycle length, stress, travel, sleep, illness, and medications. Even with regular cycles, the exact day can shift. Treat results as ranges that help you plan, not guarantees.

How this calculator estimates dates

• Ovulation day: Approximated as LMP + (cycle length − 14).
• Fertile window: The five days before ovulation plus ovulation day (you can choose 5–7 days).
• Probabilities: Higher in the two to three days before ovulation, then drop quickly after ovulation.

Fertile window explained

Sperm may survive up to several days in cervical mucus, while the egg is viable for a short period after ovulation. That’s why the days leading up to ovulation are often the most fertile.

Common ovulation signals

• Cervical mucus: Becomes clearer, stretchier (egg‑white consistency) near ovulation.
• Basal body temperature: Rises slightly after ovulation.
• OPK tests: Positive result indicates an LH surge that often precedes ovulation by 24–36 hours.

Practical planning tips

• Track consistently: Record LMP dates, cycle length, and any positive OPK results.
• Think in windows: Plan across the fertile range rather than one day.
• Stay flexible: Recalculate if your cycles lengthen or shorten.

Safety and limitations

This educational tool supports global use and does not replace medical advice. Medication, conditions, or postpartum cycles may alter timing—consult a qualified professional for personalized guidance.

Frequently asked questions

• HOW TO calculate my ovulation day from LMP? Subtract 14 from your cycle length, then add that number of days to the first day of your last period.
• HOW TO find my most fertile days? Focus on the two to three days before ovulation and ovulation day—the calculator highlights this peak.
• HOW TO use the fertile window if my cycle changes? Update your average cycle length and recalculate; compare recent months for trends.
• HOW TO track ovulation without devices? Combine cycle dates with cervical mucus observations; optionally add basal temperature to confirm after ovulation.
• HOW TO interpret the doughnut chart? It shows the percentage share of likelihood across window days; larger slices indicate higher relative chances.