How is the due date calculated?

Naegele's rule adds one year, subtracts three months, and adds seven days to the first day of the last menstrual period (LMP). For cycle length adjustment: due date = LMP + 9 months + 7 days - (cycle length - 28). Range: ±2 weeks normal (±3 weeks for irregular cycles).

How accurate is the due date?

Ultrasound in the first trimester is the most accurate method (±5-7 days). LMP-based due dates are accurate within ±2 weeks for about 80% of pregnancies. Only about 5% of babies are born exactly on their due date.

Pregnancy Due Date Calculator

Estimate your expected delivery date (EDD) based on the first day of your last menstrual period (LMP) using standard clinical obstetric algorithms.

Choose your calculation method:
1. Last Menstrual Period (LMP): First day of your last period
2. Conception Date: Day of conception (if known)
3. IVF Transfer Date: Embryo transfer day (3-day or 5-day embryo)

Cycle Length: Default is 28 days; adjust if yours is typically longer or shorter

Last Menstrual Period (LMP) Date Required for LMP method; use format MM/DD/YYYY

Conception Date Optional. Day sexual intercourse resulted in conception

IVF Transfer Date

Transfer Type

Transfer Date

Cycle Length (days) A 28-day cycle is the default. Adjust if your cycles are typically longer or shorter.

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Estimated Due Date

What Is a Pregnancy Due Date Calculator?

A Pregnancy Due Date Calculator is a specialized clinical reference tool designed for expectant mothers and healthcare observers to track gestational progress and maternal nutritional needs. By evaluating key developmental parameters such as the last menstrual period, conception timing, or pre-pregnancy baseline metrics, it provides evidence-based estimates to support healthy prenatal planning. All outputs are educational estimates and do not replace professional obstetrical ultrasound or clinical prenatal care.

How to Use This Calculator

Select the first day of your last menstrual period (LMP).
Adjust your average menstrual cycle length (standard default is 28 days).
Click 'Calculate Due Date' to view your estimated delivery date and current gestational progress.

How This Calculator Works

The calculator applies Naegele's rule, a clinical standard used by obstetricians worldwide. By adding 280 days (40 weeks) to the first day of your last normal menstrual cycle, it predicts your 40-week gestational endpoint.

Understanding Your Results

Only about 4% to 5% of babies arrive precisely on their calculated due date. The vast majority of healthy term deliveries take place between 37 weeks and 41 weeks of gestation. An ultrasound performed during the first trimester may provide a slightly revised due date from your healthcare provider.

Frequently Asked Questions

How accurate is a pregnancy due date calculator?

A due date calculation provides an estimated timeframe based on a standard 280-day gestational window. While only a small fraction of babies deliver on the exact date, it offers an accurate reference benchmark for prenatal screening milestones.

What if my menstrual cycles are irregular?

If your cycles vary significantly from 28 days, cycle-length adjustments help calibrate the estimate. In clinical practice, early first-trimester crown-rump length (CRL) ultrasound imaging provides the most accurate confirmation of gestational age.

Can my estimated due date change during pregnancy?

Yes. Obstetricians may adjust your official clinical due date if an early dating ultrasound differs from your menstrual dates by more than five to seven days.

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Important Limitations & Medical Disclaimer

Notice: This pregnancy due date calculator is intended strictly for educational and informational purposes. Due dates are approximations and do not replace formal dating ultrasound evaluations or medical care from an obstetrician or midwife.