—
estimated due date
Current gestational age—
Trimester—
Estimated conception—
How This Due Date Calculator Works
Uses Naegele's Rule — adding 280 days (40 weeks) to the first day of your last period, assuming a 28-day cycle.
Naegele's Rule
Due Date = First Day of LMP + 280 days. Your doctor may adjust based on an early ultrasound for irregular cycles.
Why Only ~5% Arrive On Due Date
It's a statistical estimate. Full term is generally 39-40 weeks, with 37-42 weeks considered normal.
Frequently Asked Questions
What if I don't know my LMP?
An early ultrasound is generally the most accurate dating method when LMP is uncertain.
Does this work for irregular cycles?
This assumes a 28-day cycle; an ultrasound is more reliable for irregular cycles.
Is this a substitute for prenatal care?
No, please consult a healthcare provider for accurate dating and care.