Pregnancy Due Date and Weeks Calculator
This pregnancy calculator uses the first day of your last period to show how far along you are, which trimester you are in and your estimated due date. You can also start from the due date if your doctor already gave you one.
The result follows the standard 40 week count and is a reference only: the dating ultrasound from the first trimester is what your prenatal team uses.
Reference calculation only. Your prenatal visit confirms the official dates.
How to use it
- Pick the first day of your last period.
- Or type the due date your doctor gave you.
- Press calculate to see weeks, trimester and due date.
Frequently asked questions
Does this replace the ultrasound?
No. The ultrasound in the first trimester is the measure your prenatal team relies on when the dates differ.
Is every pregnancy exactly 40 weeks?
Forty weeks is the reference count, but babies are considered full term between 37 and 42 weeks.
Can I use this with IVF dates?
For IVF the embryo transfer date is used instead of the last period, so the due date is calculated differently. Ask your clinic for the reference date.
This content is informational and does not replace medical care.