Ovulation Calculator

Unlike sperm, which can wait around for up to five days, an egg survives for less than a day after ovulation. That asymmetry creates a roughly six-day fertile window each cycle — and outside it, conception cannot happen. Knowing where that window falls is the single most useful thing a calendar can tell you when you are trying to conceive.

This calculator estimates ovulation as 14 days before your next expected period, because the second half of the cycle (the luteal phase) is fairly constant at about 12–14 days for most women, even when total cycle length varies. Enter your average cycle length for the best estimate — if your cycles vary, use the average of your last three.

Your body gives its own signals: cervical mucus becomes clear, slippery and stretchy (often compared to raw egg white); your basal body temperature rises by about 0.2–0.5°C (0.4–1.0°F) the day after ovulation; and some women feel a brief one-sided twinge called mittelschmerz. Ovulation predictor kits, which pick up the LH hormone surge a day or two before the egg is released, are the most practical at-home confirmation.

If you have been trying for 12 months without conceiving (or 6 months if you are over 35), or your cycles are very irregular or absent, it is worth speaking to a doctor — many causes are straightforward to investigate and treat.