How is the ovulation date calculated

Patient's question:

My menstrual cycle is 40-50 days. Please tell me if the ovulation period is calculated from the first day of menstruation to around the 14th day, or from about 14 days before the next menstrual period. Could you please help me determine my specific ovulation date? Thank you

Doctor's answer:

Hello! Intercourse during the ovulation period is the easiest way to get pregnant. Under normal circumstances, women with a regular menstrual cycle usually ovulate around 14 days before the next period. The 10-day period from 5 days before ovulation to 4 days after ovulation is the fertile window, also known as the ovulation period. Women with irregular periods are advised to do ovulation testing.
The ovulation period is about 14 days before the next period.