Ovulation Calculator

Timing intercourse around ovulation significantly increases the chance of conception. The Ovulation Calculator identifies your most fertile days based on your cycle data, giving you a clear window to focus on when trying to conceive. How to use it: Enter the start date of your last menstrual period and your average cycle length. Click Calculate to see your predicted ovulation date, your fertile window, and projections for the next 3 months. Understanding ovulation timing: Ovulation typically occurs 14 days before the start of the next period — not 14 days after the last period started, which is a common misconception. For a 28-day cycle, ovulation falls around day 14. For a 35-day cycle, around day 21. The calculator accounts for your actual cycle length to place ovulation correctly. Your fertile window: An egg survives only 12–24 hours after release. However, sperm can survive in the reproductive tract for up to 5 days. This means conception is possible in the 5 days before ovulation and on ovulation day itself — a 6-day window each cycle. The calculator highlights the full fertile window, with the peak 2 days (the day before and day of ovulation) marked separately as highest probability days. 3-month projection: The results show your ovulation dates and fertile windows for the next 3 cycles, helping you plan ahead. Each month's window is displayed with start and end dates. Signs of ovulation to watch for: While the calculator gives date estimates, physical signs confirm ovulation: a slight increase in basal body temperature (about 0.2°C) after ovulation, clear stretchy cervical mucus (described as egg-white consistency) around ovulation, and sometimes mild one-sided cramping (mittelschmerz). Ovulation predictor kits (OPKs) detect the LH surge that precedes ovulation by 24–36 hours and provide the most direct confirmation. Cycle irregularity affects accuracy — for cycles that vary more than 5 days between months, tracking physical signs alongside calendar prediction gives better results.