Due Date Calculator
Estimate your due date from your last period, a known conception date, or an IVF embryo transfer date.
Default is 28 days
Estimated due date
March 22, 2027
What Your Result Means
Your estimated due date marks 40 weeks of pregnancy. Different starting points - last period, conception, or an IVF transfer - all lead to the same due date when calculated correctly, since each method accounts for the time already elapsed before that reference point.
How It Is Calculated
LMP: due date = LMP + 280 days
Conception: due date = conception + 266 days
IVF (5-day transfer): due date = transfer date + 261 days
IVF (3-day transfer): due date = transfer date + 263 days
Worked Example
A last period starting January 1st gives an estimated due date of October 8th.
Important Assumptions
- LMP-based estimates assume a 28-day cycle by default, adjustable if your cycle differs.
- IVF due dates are based on standard embryo age at transfer (day 3 or day 5).
- Only about 5% of babies arrive on their exact estimated due date - this is a planning estimate.
Frequently Asked Questions
- Which method is most accurate?
- A known conception date or IVF transfer date gives the most precise estimate, since there's no guesswork about ovulation timing. An early ultrasound from your doctor is typically the most accurate of all.
- Why do IVF due dates use different day counts?
- A day-5 (blastocyst) transfer embryo is already 5 days past conception at transfer, and a day-3 embryo is 3 days past conception - so fewer days are added to reach the standard 266-day conception-to-due-date span.
Related Calculators
Methodology
This calculator uses Naegele's rule and standard IVF dating conventions. See our methodology page for details.
This calculator provides estimates for educational purposes only. It does not provide medical diagnosis and is not a substitute for professional medical advice. Consult a qualified healthcare provider about your health.