Due Date Calculator
Enter your values below and click Calculate for instant results.
Calculate your estimated due date from LMP, conception date, or IVF transfer. Includes IVF day-3 and day-5 embryo methods.
Enter your values below and click Calculate for instant results.
This calculator estimates your baby's due date based on one of four starting points: last menstrual period, conception date, or IVF embryo transfer date. The standard method uses the last menstrual period and adds 280 days (40 weeks). When the conception date is known, 266 days are added from that date instead.
Due dates are estimates, not guarantees. A full-term pregnancy is any delivery between 39 weeks and 40 weeks 6 days. Early term is 37 to 38 weeks 6 days. Late term is 41 weeks. Post-term is 42 weeks or beyond. Only about 5% of babies arrive on their calculated due date.
For pregnancies resulting from in vitro fertilization, the due date calculation differs from a natural conception. A Day 3 embryo transfer uses the transfer date plus 263 days. A Day 5 (blastocyst) transfer uses the transfer date plus 261 days. These offsets account for the difference between the fertilization date and the gestational age calculation used in standard obstetric care.
An early ultrasound (typically performed between 8 and 14 weeks) is the most accurate way to confirm gestational age and establish a due date. Ultrasound dating is especially important for people with irregular cycles or uncertain LMP dates. If the ultrasound date differs from the LMP-based estimate by more than about a week, providers generally adjust the due date to match the ultrasound measurement.