estimated date of delivery calculator

What is an estimated date of delivery?

The estimated date of delivery (EDD) is the projected day your baby is expected to be born. Most pregnancies are measured as 40 weeks (280 days) from the first day of the last menstrual period. Because ovulation and implantation vary, this is always an estimate rather than an exact prediction.

In clinical practice, your provider uses this date to track fetal growth, schedule screenings, and decide timing for prenatal tests. This calculator is designed to give you a practical estimate using common medical dating methods.

How this due date calculator works

1) Last menstrual period (LMP)

This is the standard method used early in pregnancy. The formula starts with the first day of your last period and adds 280 days. If your average cycle is longer or shorter than 28 days, the estimate is adjusted.

2) Conception date

If you know your conception date, the calculator adds 266 days (38 weeks). This method can be useful when conception timing is clear, such as with ovulation tracking.

3) IVF transfer date

IVF dating is often more precise because transfer timing is known exactly. The due date is calculated based on transfer day plus embryo age (for example, day-3 vs day-5 transfer).

What your result includes

• Estimated due date in full date format
• Current gestational age in weeks + days
• Pregnancy progress toward 40 weeks
• Trimester milestones for planning prenatal care

Why due dates can change

Even with accurate tracking, the EDD may shift during prenatal care. Early ultrasound measurements can refine the estimated gestational age, especially if cycles are irregular or LMP is uncertain.

• Irregular menstrual cycles
• Uncertain ovulation timing
• Variation in implantation timing
• Ultrasound findings that suggest a different gestational age

Pregnancy timing basics

Trimesters at a glance

• First trimester: Week 1 to week 13 + 6 days
• Second trimester: Week 14 to week 27 + 6 days
• Third trimester: Week 28 to delivery

Babies born between 39 and 40 weeks are considered full term in most cases. Labor can start naturally before or after the EDD and still be normal.

Tips for using an EDD calculator effectively

• Use the first day of your period, not the last day
• Enter your average cycle length honestly if your cycles are not 28 days
• If you had IVF, use the embryo transfer method for best accuracy
• Confirm all dates with your prenatal provider at your first visit

Frequently asked questions

Is the due date exact?

No. It is an estimate. Only a small percentage of babies are born exactly on their calculated due date.

Can I calculate due date without LMP?

Yes. If you know conception or IVF transfer date, those methods are often more reliable than uncertain LMP data.

What if I am already past my due date?

Going beyond 40 weeks can happen. Your provider may monitor fetal movement, fluid levels, and placental function to determine next steps.

Final note

This estimated date of delivery calculator is a helpful planning tool for prenatal appointments, maternity leave preparation, and personal milestone tracking. For diagnosis, treatment, or medical decisions, always consult your obstetrician, midwife, or qualified healthcare professional.