This calculator follows standard formulas used by obstetricians and gynecologists across the world. It supports due dates based on LMP, conception, IVF, and ultrasound adjustments.
1. LMP Due Date Method
The most commonly used approach in clinics.
Formula:
EDD = LMP + 280 days (40 weeks)
Use this if you clearly remember your last menstrual period. This method also helps calculate gestational age and pregnancy weeks using LMP.
2. Conception Date Method
Best suited if you track your ovulation or know your exact conception date.
Formula:
EDD = Conception Date + 266 days (38 weeks)
This method often gives a very precise estimate because it starts from actual fertilization timing.
3. IVF / Fertility Treatment Method
IVF pregnancies follow specific rules based on embryo age:
- Day-3 embryo transfer → add 263 days
- Day-5 embryo transfer → add 261 days
This gives a highly accurate IVF due date because the fertilization and implantation timeline is known.
4. Ultrasound Measurement Method
Early ultrasound, especially in the first trimester, can adjust your due date based on the CRL (crown-rump length).
Your doctor may revise the expected delivery date if ultrasound measurements differ from your LMP values.
Accuracy of the Due Date
Most babies arrive between 38 and 42 weeks.
This tool follows global medical standards and provides:
- A reliable EDD estimate
- Pregnancy weeks
- Trimester position
However, medical evaluation always finalizes the due date.
