How accurate is this calculator?+
This calculator provides an estimate based on the average luteal phase (14 days) and your reported cycle length. Actual ovulation can vary by several days even in regular cycles, and many factors (stress, illness, weight changes) can shift timing. For more accurate tracking, use ovulation predictor kits (OPKs) or basal body temperature charting alongside this tool.
What is the fertile window?+
The fertile window is the 6-day period when pregnancy is possible: the 5 days before ovulation (when sperm can survive in the reproductive tract) plus ovulation day itself. The highest pregnancy probability is on the day of ovulation and the 2 days before it. After the egg is released, it can only be fertilized within 12–24 hours.