Accurately predict your next period with our free period calculator . Track your cycle, plan ahead, and get personalized insights. Period Calculator Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can calculate the beginning of period ( menstrual cycle ) dates for the next 12 calendar months. You can note down the dates for your use in a private period tracker. A free, private online period tracker and ovulation calculator . Instantly track your menstrual cycle , predict future periods, and identify fertile days. No app download needed. Next period calculator Period calculators predict when your next period will start by using simple information about your menstrual cycle . Input the date of your last period , how long it lasted, and your cycle length to find out future period days and when you might ovulate.