Baby Centre Due Date Calculator

Pregnancy due dates are calculated based on the first day of your last menstrual period (LMP) or the date of a confirmed ultrasound. This calculator helps you estimate your baby's due date and understand key pregnancy milestones.

How to Use This Calculator

To calculate your due date:

Enter the first day of your last menstrual period (LMP) or the date of your confirmed ultrasound.
Select whether you're using the LMP method or ultrasound date.
Click "Calculate" to see your estimated due date.

The calculator uses the standard 40-week pregnancy period (280 days) for calculations. This is the average length of pregnancy, though individual pregnancies may vary.

How Due Dates Are Calculated

There are two main methods for calculating due dates:

Last Menstrual Period (LMP) Method

The LMP method adds 280 days (40 weeks) to the first day of your last menstrual period to estimate your due date. This is the most common method used when an ultrasound isn't available.

Ultrasound Date Method

When you have an ultrasound, your healthcare provider will calculate your due date based on the gestational age determined by the ultrasound. This method is more precise than the LMP method.

Note: Due dates are estimates. Individual pregnancies may vary by several days or weeks. Always consult with your healthcare provider for personalized advice.

Due Date = LMP Date + 280 days or Due Date = Ultrasound Date + (280 - Gestational Age in Days)

Important Pregnancy Dates

Knowing key dates in your pregnancy can help you track your progress and prepare for each stage. Here are some important milestones:

First Trimester (Weeks 1-12)

Week 1: Implantation and early development
Week 4: First ultrasound (transvaginal)
Week 8: Nuchal translucency screening
Week 12: First trimester screening

Second Trimester (Weeks 13-27)

Week 16: Anomaly scan
Week 20: Quickening (baby's first movements)
Week 24: Dating scan
Week 27: Second trimester screening

Third Trimester (Weeks 28-40)

Week 32: Non-stress test
Week 34: Group B Streptococcus (GBS) screening
Week 36: Third trimester screening
Week 37: Final ultrasound

Common Questions About Due Dates

How accurate are due date calculations?

Due dates are estimates based on average pregnancy lengths. Individual pregnancies may vary by several days or weeks. Ultrasound dates are more precise than LMP-based estimates.

Can my due date change during pregnancy?

Yes, your due date can change if your baby is born early or if your pregnancy progresses more slowly than expected. Always consult with your healthcare provider for personalized advice.

What if I don't remember my last menstrual period?

If you don't remember your LMP, you can use the date of your confirmed ultrasound or ask your healthcare provider for an estimate.

How do I know if my baby is on track?

Regular prenatal checkups, growth scans, and monitoring your baby's movements can help you track your pregnancy progress. Your healthcare provider can provide personalized guidance.