Health
Pregnancy Due Date Calculator
Estimate your due date and current week of pregnancy from the first day of your last menstrual period.
How this is calculated
Uses Naegele’s rule: the due date is estimated as 280 days (40 weeks) after the first day of your last menstrual period, assuming a typical 28-day cycle.
Why your doctor’s date may differ
If your cycle is longer or shorter than 28 days, or ovulation happened later than day 14, the real date shifts. An early ultrasound measures the baby directly and is generally more accurate, so your provider may adjust the date.
Estimate only — always confirm with a healthcare provider.