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Note: The results of this calculator are estimations based on averages for a single pregnancy. Results for a twin or multiple pregnancy will differ.
This calculator estimates a pregnancy due date using whichever information you have — the first day of your last period, an ultrasound date with gestational age, a known conception date, or an IVF transfer date. Each method adjusts the calculation slightly to give the most accurate estimate based on your specific situation.
Note: this is an estimate based on average pregnancy length (40 weeks from the last period) — your doctor's estimate based on an ultrasound is generally more precise for your specific pregnancy.
The due date, also known as the estimated date of confinement, is an estimation of when a pregnant woman will deliver her baby. While the due date is often estimated as a single date, only about 4% of births occur exactly on it — it is best treated as the center of a range.
The default method bases the calculation on the last menstrual period (LMP), assuming childbirth occurs on average 280 days (40 weeks) of gestational age from the LMP. Cycle length can also be factored in: a longer-than-average cycle shifts ovulation, and therefore the due date, later.
Due dates can also be estimated from an ultrasound (comparing fetal growth to typical growth curves), a known conception date, or an IVF embryo transfer date, which tends to be the most precise method since the exact transfer date is known.
The due date, also known as the estimated date of confinement, is an estimation of when a pregnant woman will deliver her baby.
Only about 4% of births occur exactly on the estimated due date, so it is best treated as the center of a range rather than an exact prediction.
The default method bases the calculation on the last menstrual period (LMP), assuming childbirth occurs on average 280 days (40 weeks) of gestational age from the LMP. Cycle length can also be factored in, since a longer-than-average cycle shifts ovulation, and therefore the due date, later.
Due dates can also be estimated from an ultrasound (comparing fetal growth to typical growth curves), a known conception date, or an IVF embryo transfer date.
The IVF embryo transfer date tends to be the most precise method since the exact transfer date is known.