Aisha K.
Mar 12, 2026
Clean layout and the results update instantly. Exactly what I needed for a quick planning check.
Health, Fitness & Wellness
Ovulation Calculator for Regular and Irregular Cycles
Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
Predict ovulation day and fertile window from cycle length and LMP. Estimates only—not a diagnosis or prescription.
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Inputs
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040
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Recommendations
Tailored to your live inputs and result—guidance only, not professional advice.
- Interpret
Treat this as a planning estimate
Primary result: Next ovulation (approx.) = 4 days. Re-run with optimistic and pessimistic inputs to understand the range—not just a single point.
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Plain-English guide
Terms & how it works
Confused by a field? Read the short definitions here while you use the tool.
Cycle length (days)
The “Cycle length (days)” value used in this tool’s formula. Adjust it to see results update live.
Days since LMP
The “Days since LMP” value used in this tool’s formula. Adjust it to see results update live.
How this calculator works
Predict ovulation day and fertile window from cycle length and LMP. Estimates only—not a diagnosis or prescription. Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after. Example: 28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
Example: 28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
When to use this Ovulation
Common use cases
- Predict ovulation day and fertile window from cycle length and LMP.
- Sanity-check with this case: 28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
- The relationship is: Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
Localized examples
- Health, Fitness & Wellness: the example on this page uses the same formula as the widget.
What you get
- Fields: Cycle length (days), Days since LMP
- Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
- Example on the page: 28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
How to Calculate Ovulation Step-by-Step
- 1Enter Cycle length (days), Days since LMP. Use the values you have, not a catalog average, unless that is all you know.
- 2Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
- 3Worked case: 28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
- 4If this number would change a drug, a diet, or a return-to-play call, take it to a clinician. The page never examined you.
Governing formula
Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
28-day cycle, day 10 since LMP → ovulation in ~4 days (day 14).
Example: set Cycle length (days) = 28, Days since LMP = 10, then read the result.
Variable definitions
- cycleLengthDays
Cycle length (days)
The “Cycle length (days)” field. Default 28; typical range 21–40.
- daysSinceLmp
Days since LMP
The “Days since LMP” field. Default 10; typical range 0–40.
- The formula (Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.) does not see labs, medications, sleep, or injury history. A clinician does.
- Nothing here is uploaded for the calculation itself.
Frequently Asked Questions
Ovulation ≈ cycle length − 14; fertile window ~5 days before + 1 after.
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Reviews & Ratings
See what others think about this tool, then leave your own rating to help improve CalculioHub.
4.8
out of 5.0
4 reviews
Daniel R.
Feb 28, 2026
Very usable on mobile. Would love a save/export option later, but the math feels solid.
Priya S.
Feb 3, 2026
The FAQ section answered my questions before I even had to search. Smooth dark mode too.
Marcus L.
Jan 19, 2026
Simple inputs, clear outputs. This replaced three bookmarks I used to juggle.
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