Ovulation Calculator
About the Ovulation Calculator
This ovulation calculator estimates your fertile window and ovulation day based on your cycle length and luteal phase. Ovulation occurs approximately 14 days before your next expected period. The fertile window spans the 5 days before ovulation plus ovulation day itself.
The Formula
Ovulation day = LMP + cycle length − luteal phase length. Fertile window = ovulation day − 5 days through ovulation day. Next period = LMP + cycle length. Sperm can survive up to 5 days in the reproductive tract, making the fertile window longer than the 24-hour ovulation period.
Frequently Asked Questions
How do I confirm ovulation actually occurred?
Ovulation predictor kits (OPKs), basal body temperature (BBT) charting, and cervical mucus tracking can help confirm ovulation. This calculator provides an estimate and may not be accurate for irregular cycles.
What if my cycles are irregular?
For irregular cycles, this estimate is less reliable. Tracking BBT or using OPKs for several months can help identify your personal pattern. A luteal phase shorter than 10 days may indicate a luteal phase defect.