How many days of my cycle are actually fertile, and how should we time intercourse?

Your fertile window is about six days, ending on the day of ovulation. Sperm can survive up to around five days in fertile cervical mucus, while the egg lives only about 12–24 hours — so the best chances are intercourse in the two days before ovulation and on the day itself. In practice: aim for intercourse every one to two days from a few days before you expect to ovulate. Ovulation test kits detect the LH surge, with ovulation usually following within about 24–36 hours. App predictions are estimates based on past cycles, not proof of ovulation — especially if your cycles vary. Perfect timing isn't needed, and it helps to keep it from becoming a chore.