A regular menstrual cycle is about 28-30 days. Ovulation occurs once a month – between day twelve and sixteen from the origin of your period. When egg released from an ovary which further travels down the fallopian tube and if the timing is right, there are chances of it to be fertilized by a male sperm. During this periods women who are planning to get pregnant so it is a perfect time with higher chances. Calculating your ovulation periods is very simple. Use free online ovulation calculator and fertility calendar tool will help you to know your best ovulation periods or most fertile days to get pregnant fast.