Fertility & Ovulation

Ovulation
Calculator

Find your ovulation date, fertile window, and OPK test start date. View 6 upcoming cycles with fertility windows highlighted and pregnancy odds by day.

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Ovulation

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Fertile Window

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OPK Start

Your Cycle Information

First Day of Last Menstrual Period

Average Cycle Length

Luteal Phase Length

days

💡 Most women have a luteal phase of 12–16 days (default: 14). Your cycle length can vary — enter your actual average.

Period Duration

Your Cycle at a Glance

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day cycle

Enter details to calculate

Your ovulation date

Period

Follicular

Fertile

Luteal

Ovulation Date

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Fertile Window

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Next Period

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OPK Test Start

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🔍 Signs of Ovulation

💧

Egg-White CM

Clear, slippery, stretchy cervical mucus — like raw egg white. The most reliable visible sign. Helps sperm travel.

🌡️

BBT Shift

Basal body temperature rises 0.2–0.5°C after ovulation and stays elevated. Confirms ovulation already occurred.

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Positive OPK

LH surge detected 24–36 hours before ovulation. Peak fertile time is in the 12–36 hours after a positive test.

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Mittelschmerz

Mild one-sided lower abdominal pain or cramping as the follicle releases the egg. Lasts minutes to a few hours.

💗

Breast Tenderness

Light breast sensitivity or fullness around ovulation due to the estrogen peak and LH surge.

🌶️

Increased Libido

Estrogen peaks near ovulation, naturally increasing libido — an evolutionary signal for peak fertility.

💧 Cervical Mucus Through Your Cycle

Period

Bleeding

Menstrual flow. CM not detectable. Not fertile.
⬜ Not Fertile

Post-Period

Dry / None

Little or no discharge. Vagina feels dry. Low fertility.
⬜ Low Fertility

Follicular

Sticky / Tacky

Thick, white, sticky. Doesn't stretch. Still low fertility.
🟡 Low Fertility

Pre-Ovulation

Creamy / Lotion

White or cream, lotion-like. Mild fertile mucus. Sperm can survive short-term.
🟡 Moderate Fertility

Ovulation

Egg-White (EWCM)

Clear, very slippery, stretches 2–3cm. Peak fertile sign. Sperm thrive in this environment.
✅ Peak Fertility

Luteal Phase

Dry or Sticky

Returns to dry or sticky post-ovulation. Progesterone creates hostile environment for sperm.
⬜ Not Fertile

Understanding Ovulation and Fertility

Ovulation is the release of a mature egg from the ovary, which can be fertilized for up to 12–24 hours. However, because sperm can survive 3–5 days in fertile cervical mucus, the fertile window extends to 6 days: the 5 days before ovulation and the day of ovulation itself.

How Ovulation Day Is Calculated

Ovulation Day = Cycle Length − Luteal Phase For 28-day cycle, 14-day luteal: Day 14 of cycle OPK Test Start = Ovulation Day − 4 (start testing 4 days early) LH Surge: 24–36 hours before ovulation Fertile Window: Ovulation − 5 days → Ovulation + 1 day Next Period: Ovulation + Luteal Phase days

Frequently Asked Questions

How many eggs are released during ovulation?

Typically only one egg is released per cycle, alternating randomly between the left and right ovary. Occasionally, two eggs are released simultaneously — if both are fertilized, fraternal (dizygotic) twins result. The trigger for double ovulation is a double LH surge, which is why some women get a second positive OPK result days after the first.

Can stress delay ovulation?

Yes — stress activates the HPA axis and can suppress the LH surge needed to trigger ovulation. This can delay ovulation by days or even weeks, effectively lengthening your cycle temporarily. Travel, illness, dramatic weight changes, intense exercise, and emotional stress are common causes of cycle variation. It's the main reason ovulation day is not always reliably on Day 14.

What is anovulation and how do I know if I'm not ovulating?

Anovulation is the absence of ovulation despite menstrual bleeding. Signs include: consistently irregular cycles (shorter than 21 days or longer than 35 days), never getting a positive OPK, no midcycle CM changes, and no BBT shift. PCOS (polycystic ovary syndrome) is the most common cause. If you suspect anovulation, blood tests (LH, FSH, progesterone) or ultrasound tracking can confirm ovulation.

Is it possible to ovulate twice in one cycle?

Yes — superfetation is the rare occurrence of a second ovulation after pregnancy has already begun, but it's extremely uncommon. More commonly, multiple eggs can be released within a 24-hour window during the same LH surge (leading to fraternal twins). Once progesterone rises after the first ovulation, a second LH surge is typically suppressed, preventing another egg from being released.

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