Pregnancy Due Date Calculator

How Does the Pregnancy Calculator Work?

Our pregnancy calculator uses established medical methods to estimate your due date. A typical pregnancy lasts approximately 40 weeks (280 days) from the first day of your last menstrual period (LMP), or 38 weeks from conception. However, only about 4% of babies are born on their exact due date, with most arriving within two weeks of the estimated date.

Calculation Methods

Last Menstrual Period (LMP)

The most common method adds 280 days (40 weeks) to the first day of your last period. This assumes a 28-day cycle with ovulation occurring around day 14. For women with irregular cycles, other methods may provide more accurate results.

Conception Date

If you know your conception date (from tracking ovulation or fertility treatments), we add 266 days (38 weeks) for a more precise calculation. This method is particularly accurate for those who closely monitor their cycle.

IVF Transfer Date

For IVF pregnancies, the calculation is highly precise since the transfer date is known exactly. We add 263 days for day-3 transfers or 261 days for day-5 transfers to estimate your due date.

Ultrasound Dating

Early ultrasounds (first trimester) are the most accurate method for determining due dates, as they measure fetal development directly. Your healthcare provider may adjust your due date based on ultrasound measurements.