MedDroidOvulation and fertile window calculator
Built by MedDroid · formulas from the standard calendar method (luteal phase of about 14 days)
Free · no sign-up · runs in your browserEstimate when you are likely to ovulate and your most fertile days for the next three cycles, using the first day of your last period and your usual cycle length.
Ovulation and fertile window calculator
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Your result
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How it works
Next period = first day of last period + your cycle length.
Ovulation ≈ next period − 14 days, because the time from ovulation to the next period (the luteal phase) is usually about 14 days.
Fertile window = 5 days before ovulation to 1 day after ovulation.
The calculator repeats this for your next three cycles. Example: last period 1 March, 28-day cycle → ovulation about 15 March, fertile window 10 to 16 March.
Related pages
Not a diagnosis. This tool gives a general estimate from a standard published formula. It is not a diagnosis and does not replace a check-up by a qualified doctor. If you feel very unwell, call your local emergency number (India: 108 or 112).
Frequently asked questions
Can I use an ovulation calculator as birth control?
No. It is only an estimate, and ovulation can come earlier or later than expected. If you want to avoid pregnancy, talk to a doctor about reliable contraception.
How do I know if I have actually ovulated?
Signs include clear, stretchy vaginal mucus and a small rise in body temperature after ovulation. Home ovulation (LH) test kits and tests by your doctor can give more detail.
What if my periods are irregular?
Calendar estimates are less reliable with irregular cycles. Conditions such as PCOS or thyroid problems can cause irregular periods, so it is worth seeing a doctor.
When should I take a pregnancy test?
Most home tests are reliable from the first day of your missed period. Testing too early can give a false negative.