How we worked it out
Updated as you change the numbers.
- Next period = last period + 28 days.
- Ovulation ≈ 14 days before the next period. Fertile window = 5 days before ovulation to 1 day after.
Method and assumptions
The luteal phase (after ovulation) is fairly constant at about 14 days, so ovulation is predicted 14 days before the next expected period. The fertile window spans the 5 days before ovulation, because sperm can survive that long, and the day after. Irregular cycles make predictions less reliable; ovulation tests or temperature tracking are more accurate.
Questions
When do I ovulate with a 28-day cycle?
About day 14, counting the first day of your period as day 1.
Sources
Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.