Is this estimation reliable?

Yes, it is the standard method used by doctors worldwide. However, actual delivery may vary by a few days.

Does it work if I have irregular cycles?

If your cycles are irregular, there might be a small margin of error. It's best to confirm with a first trimester ultrasound.

How is the due date calculated?

Q: How is the due date calculated?

The estimated due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period.

The estimated due date is a prediction of when your baby might be born. It’s calculated by adding 280 days (40 weeks) to the first day of your last menstrual period. This method is known as Naegele’s Rule and is widely used by doctors and obstetricians.

While labor can occur a few days before or after, this date serves as an excellent reference for scheduling checkups, exams, and preparing for your baby's arrival.

With this tool, you can calculate in seconds:

Your estimated due date
The day of the week your baby may be born
A clear reference point to follow your pregnancy calendar

🛠️ How to use the Due Date Calculator

You only need to enter the first day of your last menstrual period. The calculator will handle the rest automatically.

The system adds exactly 280 days to that date and gives you:

The estimated due date in day-month-year format
The name of the weekday (Monday, Tuesday, etc.)

💡 Tip: This tool doesn’t replace an ultrasound but is helpful to begin prenatal care from day one.

📊 Understanding your result

The result is a statistical estimate. Only a small percentage of women give birth on their exact due date.

Delivery can happen a few days before or after
Pregnancy is considered full-term between weeks 37 and 42
Your OB/GYN may adjust the date based on ultrasounds

This information is still very useful to plan other important milestones like ultrasounds, lab tests, and delivery preparation.

❓ Frequently Asked Questions

What if I don’t remember the exact date?

You can enter the closest possible date. The tool will provide an estimated result, but it’s best to confirm it clinically.

Can I use it without a regular cycle?

For irregular or absent cycles, an early ultrasound is needed to properly estimate the due date.

Does this replace a medical appointment?

No. It’s a helpful guide for estimating, but it doesn’t replace professional prenatal care.

What method does this calculator use?

It uses Naegele’s Rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. It’s the medical standard.

✅ Conclusion and Related Tools

Knowing your estimated due date is key to beginning prenatal care, organizing your medical appointments, and preparing emotionally for childbirth.

You can also combine this with other tools available on CalcFit: