Estimate ovulation from your cycle
Bare “ovulation calculator” is a KD70 megaserp. We still help: ovulation ≈ LMP + (cycleLength − 14), with a fertile window around it. Title and H1 stay cycle-framed on purpose. Estimate only — not medical advice.
Enter a date to see an estimate.
What this page does
Period start + average length → rough ovulation and fertile window, plus a planning EDD if conception happened on that ovulation day (+266).
Will not beat a well-timed OPK. Will not retitle to naked “Ovulation Calculator” for greed.
When to use
Rough timing without OPKs; bridging into due date from ovulation if pregnancy happens.
When not to
Clomid/trigger cycles with clinic instructions. Contraception. Claiming false precision.
Assumptions
Browser-only planning arithmetic. Defaults are disclosed on the page. Ultrasound and clinic policy override this tool.
Examples
LMP Aug 1, 2026 · cycle 28 → Ovulation ≈ Aug 15 · window Aug 10–15.
LMP Aug 1, 2026 · cycle 35 → Ovulation ≈ Aug 22 · window Aug 17–22.
Gotchas
Clinic dating after ultrasound can differ from browser math — the clinic wins for medical decisions.
Wrong input dates (retrieval vs transfer, spotting vs true LMP) slide every result.
Estimate only — not medical advice.
How this is calculated
The math stays in your browser. Enter the dates you actually know, read the estimate, and treat clinic ultrasound dating as the authority when it disagrees.
Nothing here is medical advice, a diagnosis, or a substitute for prenatal care.
- Enter the date(s) or numbers this page asks for.
- Check the assumptions under the result and on Methodology.
- Compare with your clinic portal if you have one.
- Use related tools if you only have a different kind of date.
- Confirm medical decisions with your clinician.
ovulation ≈ LMP + (cycle − luteal); fertile ≈ ovulation−5 … ovulation; EDD ≈ ovulation + 266.
Related calculators
Menstrual cycle calculator · luteal phase · ovulation → EDD · implantation. We refuse the bare ovulation-calculator Primary fight.
See also: menstrual cycle calculator, ovulation to due date calculator, and implantation calculator.
FAQ
- How do you estimate ovulation from cycle length?
- Often cycle length minus ~14 days from LMP.
- As accurate as OPKs?
- Usually no.
- Why not target “ovulation calculator”?
- Head term is dominated; cycle-based estimates still help.
- Birth control?
- Not the intended use.
- Variable luteal length?
- Breaks the −14 rule.
- Is this medical advice?
- Estimate only — not medical advice. Confirm dating, testing, and medical decisions with your clinic.