What Is a Pregnancy Due Date Calculator?
A pregnancy due date calculator estimates the expected delivery date based on the first day of your last menstrual period (LMP). Using Nägele’s rule—a standard obstetric method—it adds 280 days (40 weeks) to the LMP to determine the estimated due date (EDD).
How to Use This Pregnancy Due Date Calculator
- Select the first day of your last menstrual period using the date picker.
- Click “Calculate” to see your estimated due date, current gestational week, trimester, days remaining, and key trimester milestone dates.
Key Concepts
Nägele’s rule assumes a 28-day cycle with ovulation on day 14. The formula is: EDD = LMP + 280 days. Only about 5% of babies are born on their exact due date; most arrive within a two-week window around the EDD. Ultrasound dating in the first trimester is generally more accurate. Always follow your obstetrician’s guidance.
Frequently Asked Questions
How accurate is the due date estimate?
The LMP-based estimate is a statistical approximation. First-trimester ultrasounds are typically accurate to ±5–7 days. Only about 5% of babies arrive on the exact due date.
What if my menstrual cycle is irregular?
If your cycles are irregular, the LMP-based calculation may be less accurate. An early ultrasound measurement can provide a more reliable estimate. Discuss with your healthcare provider.
Does this replace medical prenatal care?
No. This tool provides an estimate for informational purposes only. Regular prenatal checkups with a qualified healthcare provider are essential for monitoring pregnancy health.