Pregnancy Calculator
Estimate due date using the first day of your last menstrual period (LMP).
Key milestones
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How the estimate works
Most due date calculators use the first day of the last menstrual period (LMP) and add 280 days (40 weeks) to estimate an expected delivery date. This is a standard obstetric method that assumes a 28-day cycle with ovulation around day 14. Not all cycles follow that pattern; variations in cycle length or ovulation timing can shift the estimated date.
The calculator also provides a current gestational age estimate by comparing today’s date to the LMP date. Gestational age is commonly used by healthcare providers to track development and schedule key screenings and appointments.
Limitations and next steps
The date provided is an estimate. Early ultrasound dating is more accurate for establishing a due date, especially if the cycle length is irregular. Use the result as a planning guide and discuss ultrasound results and prenatal care timelines with your care provider for the most reliable information.