Calculate your pregnancy due date using last menstrual period (LMP), conception date, or ultrasound. Track trimesters, milestones, and fetal development. 100% private — all in your browser.
A due date calculator estimates when your baby will be born based on your pregnancy timeline. The most common method uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This calculator also supports alternative methods like conception date (+266 days) and ultrasound dating, which can be more accurate if you know the exact date. Remember that only about 5% of babies are born on their exact due date — most arrive within a week before or after.
Due date calculators provide an estimate based on standard medical formulas. LMP-based calculation is accurate within ±2 weeks for most women with regular 28-day cycles. Ultrasound dating in the first trimester is the most accurate method, typically within ±5 days.
Naegele's Rule is a standard method for estimating due date: add 1 year, subtract 3 months, and add 7 days to the first day of the last menstrual period. This equals approximately 280 days or 40 weeks from LMP.
Yes. If your early ultrasound dating differs significantly from your LMP-based estimate (by more than 7 days), your healthcare provider may adjust your due date based on the ultrasound measurements, which are more precise in early pregnancy.
Due date is an estimate, not a deadline. A normal pregnancy can range from 37 to 42 weeks. Your baby's development, your cycle length, and individual biological variations all influence the actual delivery date.
If you don't know your LMP, use the conception date method (if known) or the ultrasound method. Many women also use ovulation tracking apps or ovulation test kits to pinpoint conception timing.