Calculate Your Estimated Due Date
Enter your conception date to estimate your baby’s due date. This method uses 266 days (38 weeks) from conception, which aligns with standard obstetric dating.
How this due date calculator works
This due date calculator by conception date estimates pregnancy due date by adding 266 days to the date conception occurred. That equals 38 weeks from conception, or 40 weeks of gestational age when counting from the first day of the last menstrual period (LMP).
Many online pregnancy tools ask for your LMP. That is useful, but if you know your conception date more precisely—such as after tracking ovulation or during IVF—using conception can provide a more direct estimate.
What you get from this calculator
- Your estimated due date based on conception date
- An estimated LMP date (conception minus 14 days)
- Pregnancy week/day today (estimated gestational age)
- Important milestone dates, including 12 weeks, 20 weeks, and full term
Why 266 days from conception?
In clinical practice, pregnancy is typically described as 40 weeks from LMP. Conception usually happens about 2 weeks after LMP in a 28-day cycle. That means:
- 40 weeks from LMP
- or about 38 weeks from conception
- or 266 days from conception
Because of this, conception-based due date calculators use the 266-day rule as a standard starting point.
Accuracy and important limitations
1) Due dates are estimates, not exact deadlines
Even with a known conception date, birth may occur before or after the estimated day. Most healthy pregnancies deliver within a date range around the due date.
2) Cycle variation matters
If conception date is estimated from cycle tracking rather than confirmed by testing or treatment timing, there may still be a margin of error.
3) Ultrasound can refine dating
Early ultrasound measurements are often used by clinicians to confirm or adjust due date estimates, especially when dates are uncertain.
Using this if you conceived with IVF
For IVF pregnancies, dates may be more precise because embryo transfer and fertilization timing are known. In those cases, your fertility team may provide a specific due date formula based on transfer day and embryo age. This tool still offers a useful quick estimate.
Frequently asked questions
Is conception date the same as ovulation date?
They are often very close. Conception usually occurs within about 24 hours of ovulation.
Can I calculate due date without LMP?
Yes. That is exactly what this conception date due date calculator does.
Is this a medical diagnosis?
No. This tool is educational and informational only. Always follow advice from your obstetrician, midwife, or fertility specialist.
Bottom line
If you know when conception happened, calculating due date can be straightforward and practical. Use this due date calculator by conception date to estimate your timeline, then confirm with your prenatal care provider for individualized medical guidance.