How do I calculate ovulation?

Regular cycles? A woman with very regular periods can estimate her ovulation day this way: mark on a calendar when her next period will begin (that means mark the first day of her next period), and just look back 2 weeks to see her estimated day of ovulation. So, if her next period will start on january 28, then january 14 is her estimated ovulation day. The estimate is +/- 2 days (life is not exact).