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Pregnancy Due Date Calculator

Enter the first day of your last menstrual period (or your conception date) and this calculator estimates your due date using the standard 280-day rule, adjusted for your cycle length — plus your current week of pregnancy, trimester dates, and the full-term window. It runs entirely in your browser: free, private, and no sign-up.

Calculate fromFirst day of last period

Average cycle length (days)

Enter the first day of your last period to see your estimated due date, trimester dates, and how far along you are.

Frequently asked questions

From your last menstrual period (LMP) it uses Naegele's rule: LMP + 280 days (40 weeks), adjusted by the difference between your average cycle length and 28 days. From a conception date it adds 266 days. Both are the standard clinical starting-point estimates.

It's an estimate, not a prediction — only a small minority of babies arrive on their exact due date, and most are born within a couple of weeks either side. An early ultrasound gives a more precise date, so always confirm your dates with your midwife or doctor.

Enter your average cycle length and the calculator shifts the estimate accordingly — ovulation typically happens about 14 days before your next period, so a 32-day cycle moves the due date about 4 days later than the standard rule.

Yes — free and no sign-up, and because everything is calculated in your browser, the dates you enter are never uploaded or stored anywhere.