Pregnancy Due Date Calculator
Estimate your baby's due date from your last period, conception date, or ultrasound.
Pregnancy Due Date Calculator
Estimate your baby's due date and track your pregnancy progress.
How to Use
Choose your calculation method
Select whether you want to use your last period, conception date, or an ultrasound.
Enter the date
Input the specific date for the method you chose.
Check your milestones
See your due date, current week, and trimester breakdown.
How is Your Due Date Calculated?
When you find out you're pregnant, the very first question is usually: "When is the baby coming?" Medical professionals almost universally use Naegele's Rule, which adds 280 days (or exactly 40 weeks) to the first day of your last menstrual period (LMP). While this sounds simple, it assumes everyone has a perfect 28-day cycle. Our calculator lets you adjust for your actual cycle length, or calculate based on your exact conception date or a recent ultrasound scan.
Real-World Examples & Use Cases
Planning Your First Doctor's Appointment
When you call to schedule your first prenatal visit, the receptionist's first question will be about your last menstrual period to calculate how far along you are. Doctors usually want to see you between 8 and 10 weeks. Using this calculator beforehand helps you know exactly when that window is, so you can schedule the appointment at the right time.
Correcting for Irregular Cycles
The standard '40 weeks' rule assumes every woman ovulates on day 14 of a 28-day cycle. If you have a 35-day cycle, you actually ovulate around day 21, which means a standard calculator will give you a due date that is a full week too early! Being able to adjust your cycle length in the calculator gives you a much more accurate timeline before you even see the doctor.
Tracking Week-by-Week Development
Pregnancy apps and books are entirely based on your 'gestational age' in weeks. Knowing whether you are 6 weeks or 7 weeks pregnant determines what developmental milestones your baby is hitting (like when the heart starts beating). Having a precise due date lets you follow along accurately.
How It Works
Here's the math behind the dates: **Using Last Menstrual Period (LMP):** Due Date = LMP + 280 days (40 weeks) If your cycle isn't 28 days, we adjust it: Due Date = LMP + 280 days + (Your Cycle Length - 28) **Using Conception Date:** Due Date = Conception Date + 266 days (38 weeks) **Using Ultrasound:** We take the date of the ultrasound, figure out how many days you had left until 280 days based on the gestational age measured, and project forward to find your due date. Keep in mind that "full term" is considered anywhere from 37 to 42 weeks, and only about 5% of babies actually arrive on their exact estimated due date!
Frequently Asked Questions
Is the due date a guarantee?▼
Why do doctors count from my last period instead of conception?▼
Will my due date change?▼
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