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When do you ovulate?

Ovulation typically occurs 14 days before your next period, not 14 days after your last period. For a 28-day cycle, this is around day 14. For a 30-day cycle, it's around day 16. The fertile window spans the 5 days before ovulation plus ovulation day itself, as sperm can survive up to 5 days.

Last updated: December 2025

Ovulation Calculator

Estimate when you're most likely to ovulate and identify your fertile window. Whether you're trying to conceive naturally or timing a natural FET cycle, understanding your ovulation is key.

Your Cycle Details

21 days40 days

Ovulation by Cycle Length

Cycle LengthOvulation DayFertile Window Starts
21 daysDay 7Day 2
24 daysDay 10Day 5
26 daysDay 12Day 7
28 daysDay 14Day 9
30 daysDay 16Day 11
32 daysDay 18Day 13
35 daysDay 21Day 16

Based on a 14-day luteal phase. Individual timing may vary.

Signs of Ovulation

Positive OPK

A positive test indicates LH surge. Ovulation typically occurs 12-36 hours after.

Cervical Mucus

Egg-white consistency (clear, stretchy, slippery) indicates peak fertility.

BBT Shift

Temperature rises 0.3-0.5°F after ovulation and stays elevated until period.

Mittelschmerz

One-sided lower abdominal pain or cramping around ovulation time.

Track Your Cycle

Use IVFPath to log your cycle, track ovulation symptoms, and get personalised fertile window predictions based on your history.

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Frequently Asked Questions

Medical Review: IVFPath Medical Content Team • Last reviewed: December 2025

Disclaimer: This calculator provides estimates based on average cycle patterns. For precise ovulation timing, use ovulation predictor kits or consult with your fertility specialist for ultrasound monitoring.