Estimate an ovulation date and fertile interval from the start of the last period and a cycle-length assumption.
Ovulation Calculator
Results
Ovulation day
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Table of Contents
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What is Ovulation Calculator?
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How to Use This Calculator
- Enter or select Cycle duration, My last period started on....
- Check the unit beside each measurement. For a percentage or rate, use the scale and time period stated in the form.
- Choose Calculate, then compare the output with the formula and example below. If you change a value or option, calculate again to update the result.
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Formula Used
Estimated ovulation ≈ next expected period−14 days.
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Variables Explained
| Input | What it means |
|---|---|
| Cycle duration | The length of the measurement or reporting interval, in the selected unit. |
| My last period started on... | Use the observed finding or laboratory value for this criterion, following the definition shown in the form. |
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Worked Example
For a 28-day cycle, the estimate lies about two weeks after the period starts.
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Why Use This Calculator?
Use the calculation to make the method and its inputs easier to check with a healthcare professional. Its meaning depends on the clinical setting and on whether the underlying method is appropriate for that person.
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Common Mistakes
- Ovulation varies between and within people. A calendar estimate is not reliable contraception or confirmation of ovulation.
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Frequently Asked Questions
Is this result a diagnosis or treatment instruction?
No. It describes a calculation or score from the supplied information. A qualified clinician must check the measurements, the method’s applicability and the wider clinical picture.
Can I enter the units from any lab report?
Use the units specified in the form and select a conversion only where the page provides one. Different substances need different conversion factors; a mismatch can produce a plausible but incorrect result.
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Sources & References
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