Most doctors calculate a due date by adding 40 weeks to the first day of your last period. The actual day of conception might be later, so most babies are born within 2 weeks of the due date. +1 vote! Initially doctors calculate your due date as 40 weeks from the first day of your last period.How do I work out my due date?
Working out your due date. To work out your due date, you need to count 40 weeks from the first day of your last period. You could even try working out your date from when you think you conceived – tricky for most women as they won't know exactly when they ovulated!How do you calculate estimated due date?
The estimated due date (EDD or EDC) is the date that spontaneous onset of labor is expected to occur. The due date may be estimated by adding 280 days ( 9 months and 7 days) to the first day of the last menstrual period (LMP). This is the method used by "pregnancy wheels".