If you are looking for a quick and practical way to estimate your pregnancy timeline, this predicted due date calculator can help. It gives you an estimated due date, gestational age, and milestone dates based on the information you provide.
How this predicted due date calculator works
This tool uses common medical dating conventions used in obstetrics. You can calculate your estimated due date from one of three starting points:
- Last menstrual period (LMP): The most common method, based on a 40-week pregnancy timeline.
- Conception date: Useful when ovulation or conception timing is known.
- IVF transfer date: A more precise method for IVF pregnancies, adjusted by embryo age.
Formulas used
- LMP method: Due date = LMP + 280 days + (cycle length − 28)
- Conception method: Due date = Conception date + 266 days
- IVF method: Due date = Transfer date + (266 − embryo age in days)
Why due dates are called “estimated”
Even with accurate dates, a due date is still an estimate. Most babies are not born exactly on that day. Many healthy pregnancies deliver within a window before or after the predicted date. This estimate is best used for planning and discussion with your prenatal care provider.
How to use the calculator
1) Select your dating method
Choose the method that best matches your information. If you are unsure, LMP is usually the starting point for most people.
2) Enter your date(s)
Use the calendar inputs to avoid formatting errors. If using LMP, also enter your typical cycle length for better personalization.
3) Review your timeline
After calculation, you’ll see:
- Estimated due date
- Estimated conception and LMP-equivalent date
- Current gestational age
- Trimester status and milestone checkpoints
Understanding gestational age vs. fetal age
Pregnancy dating is generally tracked from the first day of your last menstrual period, not from the day of conception. That means gestational age is typically about two weeks ahead of fetal age in naturally conceived pregnancies.
What can affect due date accuracy?
- Irregular cycles or uncertain LMP date
- Late or early ovulation
- Implantation timing differences
- Dating adjustments from ultrasound in early pregnancy
Early ultrasound is often considered the most accurate way to confirm or refine dating, especially if menstrual history is uncertain.
Frequently asked questions
Is this calculator a diagnosis tool?
No. It is a planning tool based on standard dating formulas. It does not replace prenatal medical care.
Can I use this if I conceived via IVF?
Yes. Use the IVF option and select embryo age at transfer (day 3 or day 5) for a more tailored estimate.
What if my due date has already passed?
The calculator will still show your estimated due date and indicate that it has passed. Your clinician can guide next steps based on your specific pregnancy and monitoring.
Important note
This predicted due date calculator is for educational use and convenience. For personalized care, confirm your dates with an obstetrician, midwife, or qualified prenatal provider.