Sperm survives up to 5 days; an egg lives about 24 hours. The fertile window is roughly the 5 days before ovulation plus ovulation day.

Ovulation typically occurs 14 days before the next period — not 14 days after the last one. Long-cycle women ovulate later than the textbook ‘day 14.’

Tracking basal body temperature or LH surge confirms ovulation; calendar methods are estimates and least accurate for irregular cycles.