Pregnancy Due Date Calculator
Estimate your due date from the first day of your last period — plus how far along you are and your estimated conception date.
Pregnancy tracking apps and resources
Learn moreHow the date is estimated
The standard estimate, Naegele’s rule, adds 280 days (40 weeks) to the first day of your last period. It assumes a 28-day cycle and ovulation around day 14, so a longer or shorter cycle shifts the date. Only about 1 in 20 babies actually arrives on the due date — it’s a center point, not a deadline.
How it’s calculated & sources
Due date = last period + 280 days, adjusted for cycle length (days beyond 28 push it later). Estimated conception is ~14 days after the last period. Current week counts from the last period.
Benchmark: Naegele’s rule (last menstrual period + 280 days), the standard obstetric dating method.
Results update as you type and are general estimates, not personalized financial, tax, medical or legal advice. Verify with a professional.
Worked example
A last period on January 1 with a 28-day cycle gives a due date around October 8, with conception estimated in mid-January.
Frequently asked questions
How accurate is the due date?
It’s an estimate — a normal birth can occur up to two weeks either side. An early ultrasound often refines the date.
What if my cycle isn’t 28 days?
Enter your cycle length and the tool shifts the date accordingly, since ovulation timing moves with cycle length.