Ovulation Window Calculator
Fertile window & ovulation date · Calendar view · Conception probability guide
Cycle information
The first day of your most recent period
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26
28
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35
40+
3 days
5 days
7 days
Regular
Slightly irregular
Irregular
Purpose
Trying to conceive
Maximise conception probability
Natural family planning
Identify days to avoid unprotected intercourse
Cycle tracking only
Understand my cycle pattern
Clinical context
♀ Ovulation typically occurs 14 days before the next period — not 14 days after the last period (unless your cycle is exactly 28 days). This calculator adjusts for your actual cycle length.
⚠ PCOS note: With PCOS, ovulation may be delayed, absent, or occur unpredictably. These dates are estimates only. A more reliable approach is to use ovulation predictor kits (OPKs) or follicle tracking ultrasound with your gynaecologist.
Please enter the first day of your last period.
Estimated ovulation date
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Ovulation day
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Fertile window
6 days
Luteal phase
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Next period est.
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Cycle calendar — current cycle
Period
Fertile window
Peak fertility
Ovulation day
Luteal phase
Today
Best days for conception — ranked by probability
Natural fertility signs to watch for
💧 Cervical mucus
Most reliable natural sign
As ovulation approaches, cervical mucus changes from dry/sticky → creamy → wet/slippery → raw egg-white (clear, stretchy). The egg-white consistency signals peak fertility. This is the single most reliable natural ovulation indicator.
🌡 Basal body temperature (BBT)
Confirms ovulation has occurred
BBT rises by 0.2–0.5°C after ovulation and stays elevated until the next period. Measure every morning before getting out of bed, at the same time. A sustained rise for 3 days confirms ovulation. Note: BBT confirms ovulation after the fact, not before.
🧪 Ovulation predictor kit (OPK)
Detects LH surge 24–36 hrs before ovulation
OPK strips (available at any chemist for ₹50–200) detect the LH surge that triggers ovulation. A positive OPK means ovulation will occur within 24–36 hours. Most accurate method of home ovulation prediction after basal temperature.
⚪ Mittelschmerz (mid-cycle pain)
Felt by about 20% of women
Some women feel a mild twinge or ache on one side of the lower abdomen around ovulation. This is caused by the follicle releasing the egg. It may last minutes to hours. Not all women experience this — its absence does not mean ovulation has not occurred.
Important notes & reminders
ⓘ For informational purposes only. Not a substitute for medical advice.
Ovulation estimation is based on the standard formula: ovulation occurs approximately 14 days
before the next expected period, adjusted for individual cycle length. This is a statistical
estimate — actual ovulation can vary by several days even in regular cycles. Women with PCOS,
thyroid disorders, breastfeeding, or stress-related cycle changes may experience significantly
different timing. For confirmed ovulation tracking, follicle monitoring ultrasound with a
gynaecologist is the most accurate method.