Calculate due date of delivery • What was the first day of your last menstrual period? Note that down. E.g. 21st November 2021 • Now, go 3 months back from the date you just noted down. Write it down. E.g. 21st August 2021 • Finally, add 1 year and 7 days to the date you noted in previous step. E.g. 28th August 2022 The answer right infront of you is only an estimate as this rule is based on ideal 28 days menstrual cycle.