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Dr. Sarah Schmidt · Medical Specialist in Gynecology and Obstetrics
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Your Ovulation Calculator
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Calculate your ovulation, fertile window, and next period start – fast, free, and without storing data on our servers.

Last medical review: 2026-03-01

Quick Answer: Quick Answer: Ovulation typically occurs approx. 14 days before the next period starts — for a 28-day cycle, that's day 14.

Typical range: 21–45 days (avg. 28 days)

For a more accurate calendar view

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Medically reviewed by
Dr. Sarah Schmidt

Specialist medical training in Gynecology, 12 years of clinical experience

Verified Health ContentUpdated: 2026-03-01

How does the calculation work?

Ovulation typically occurs approx. 14 days before your next period. In a standard 28-day cycle, this happens on Day 14.

Our tool uses the standard clinical formula:

Ovulation = LMP + (Cycle Length − 14)
Fertile Window = Ovulation − 5 → Ovulation + 1

This is based on identifying the Luteal Phase, which remains consistent (approx. 14 days) even when the first half of your cycle varies. Full methodology →

Calculation by Cycle Length

Direct estimation for your specific cycle length:

25 Day Cycle26 Day Cycle27 Day Cycle28 Day Cycle29 Day Cycle30 Day Cycle31 Day Cycle32 Day Cycle

Frequently Asked Questions

Ovulation is typically calculated by subtracting 14 days from the expected start of your next period. For a 28-day cycle, ovulation usually occurs on day 14. This is based on the biological fact that the luteal phase (the time after ovulation) is relatively constant at 14 days.
This tool provides a reliable estimate for regular cycles (±1–2 days). If your cycles are irregular, the prediction may be less precise. It should be used as a guide and is not a substitute for medical grade ovulation tests or professional medical advice.
The fertile window lasts about 6 days: the 5 days before ovulation and the day of ovulation itself. This is because sperm can live inside the female body for up to 5 days, while the egg is viable for about 12-24 hours.
No. This calculator is designed to help you identify your most fertile days to *increase* chances of conception. It is not suitable for contraception as individual cycles can vary due to stress, illness, or hormonal changes.
Zero data storage. All calculations happen locally in your browser. Your reproductive health data never leaves your device and is never sent to our servers.