Planning a baby? An ovulation calendar can help you increase your chances of conceiving a baby boy or a girl by predicting the gender of your baby based on where you are in your ovulation cycle. You may use one of multiple free software options on web sites to achieve your desired results. Sperm carrying X-chromosomes lives longer and swims slower than male Y-carrying sperm. Therefore, if you have intercourse about 3 days prior to ovulation, you have a better chance of conceiving a girl. Contrary, the closer to ovulation you have sex, the better the chances are of having a boy. To use the ovulation calendars you need to enter: the first day of your last period, the length of your menstrual cycle, and the length of your luteal phase. If you don’t know exactly your luteal phase length, you may use an average length of 14 days. If you have a gender preference, simply select boy or girl from the gender field.