How the ovulation calculator works
- Ovulation = first day of your last period + cycle length − 14 days.
- Fertile window = the five days before ovulation, plus ovulation day.
- Next period = first day of your last period + cycle length.
- Due date = first day of your last period + 280 days, moved by how much your cycle differs from 28 days.
Already pregnant? Find your due date and week by week with the due date calculator.