Enter your last period date and cycle length to predict your ovulation day, fertile window, and the best days to conceive — for the next 6 months.
Next 6 months forecast
Important: This calculator estimates ovulation based on average cycle data and is for informational purposes only. Individual cycles can vary significantly. This tool must not be used as a form of birth control or as a substitute for clinical fertility evaluation. Consult your healthcare provider for personalized fertility or contraception guidance.
Ovulation is the release of a mature egg from one of your ovaries. It typically occurs about 14 days before your next period begins, regardless of your total cycle length. For a 28-day cycle, that's around day 14. For a 35-day cycle, it's around day 21.
The egg survives for 12–24 hours after release. Sperm can survive up to 5 days inside the reproductive tract. This means your fertile window is approximately 6 days: the 5 days before ovulation plus the day of ovulation itself. This ovulation calculator predicts that window based on your cycle data.
Your body provides several signals around ovulation that you can learn to track. Cervical mucus becomes clear, slippery, and stretchy — similar to raw egg whites — in the days leading up to ovulation. This is your most fertile mucus type, designed to help sperm travel to the egg.
Basal body temperature (BBT) rises by about 0.2–0.5°C after ovulation due to increased progesterone. By the time you see the temperature rise, ovulation has already occurred — making BBT useful for confirming ovulation patterns over multiple cycles rather than predicting the current one.
Some women experience mild pelvic pain (mittelschmerz) on one side during ovulation, lasting a few minutes to a few hours. Ovulation predictor kits (OPKs) detect the LH surge that occurs 24–48 hours before ovulation and are the most reliable way to predict it in advance.
Ovulation calculators provide estimates based on average cycle patterns. They work best for women with regular cycles (21–35 days). For irregular cycles, the prediction may be less accurate. Combining calculator results with physical signs (cervical mucus, BBT) or ovulation predictor kits gives the best results.
It's very unlikely. The egg survives only 12–24 hours after ovulation, and sperm can live up to 5 days. Outside the 6-day fertile window, conception is extremely rare. However, cycle timing can vary, which is why this calculator should not be used as birth control.
The highest conception rates occur when intercourse happens 1–2 days before ovulation. The day of ovulation itself is also fertile, but slightly less so because the egg has a short lifespan. Having intercourse every other day during your fertile window maximizes your chances.
The second half of your cycle (after ovulation) is relatively fixed at about 14 days. The first half varies. So a 28-day cycle typically ovulates on day 14, a 32-day cycle on day 18, and a 35-day cycle on day 21. This calculator adjusts for your actual cycle length.
If your cycles vary by more than 7–8 days from month to month, predictions become less reliable. Consider tracking cervical mucus and using OPKs instead. Irregular cycles can sometimes indicate conditions like PCOS — consult your healthcare provider if your cycles are consistently irregular.