Pregnancy Due Date Calculator
Estimate your baby’s due date using one of three common methods: last menstrual period (LMP), conception date, or IVF embryo transfer date.
How a pregnancy due date calculator works
A pregnancy due date calculator estimates when your baby may be born. The most common estimate is based on a 40-week pregnancy, counted from the first day of your last menstrual period (LMP). This method is often called Naegele’s rule.
Because every person and every pregnancy is different, an estimated due date (EDD) is not a guarantee. It is best treated as a target window, not an exact appointment.
Three common ways to estimate due date
- LMP method: Adds about 280 days (40 weeks) to the first day of your last period, with optional cycle-length adjustment.
- Conception date method: Adds about 266 days (38 weeks) to the date of conception.
- IVF method: Uses embryo transfer date plus embryo age at transfer to determine gestational timeline.
Step-by-step: using this due date calculator
1) Pick your method
Choose the input type that is most accurate for your situation. If you know your transfer date from IVF, that method is usually very precise. If not, LMP is widely used in early pregnancy care.
2) Enter your date(s)
Enter your date carefully. A one-day error can shift milestones such as first trimester end, anatomy scan timing, and expected delivery week.
3) Click “Calculate Due Date”
The result will show your estimated due date, estimated gestational age today, trimester, and key milestone dates.
Understanding your result
Estimated due date (EDD)
Your EDD is a planning point for prenatal care. Most babies are born between 37 and 42 weeks, and only a small percentage are born exactly on their due date.
Gestational age vs fetal age
- Gestational age: Counted from LMP (clinical standard).
- Fetal age: Counted from conception (about two weeks less than gestational age).
Trimester overview
- First trimester: 0 weeks to 13 weeks 6 days
- Second trimester: 14 weeks to 27 weeks 6 days
- Third trimester: 28 weeks to birth
What can change a due date?
Early ultrasound can revise your expected date, especially if cycle history is uncertain. Your provider may adjust EDD if measurements suggest a different timeline.
- Irregular menstrual cycles
- Uncertain LMP date
- Late ovulation
- Early ultrasound findings
- Assisted reproductive technologies (IUI/IVF)
Important reminders for prenatal planning
- Schedule prenatal visits as early as possible.
- Discuss any bleeding, severe pain, fever, or concerning symptoms with your clinician right away.
- Use your due date estimate as guidance for appointments, classes, leave planning, and support preparation.
Frequently asked questions
Is this calculator 100% accurate?
No. It provides an estimate, not a diagnosis. Medical dating scans and provider assessment are more definitive.
Which method is most accurate?
IVF transfer dating is typically very accurate. For natural conception, early first-trimester ultrasound usually provides the best clinical estimate when LMP is uncertain.
Can I deliver before or after my due date and still be normal?
Yes. Many healthy pregnancies deliver before or after the estimated due date. Your care team will monitor your health and your baby’s health to determine safest next steps.
Medical disclaimer
This due date calculator is for educational use and does not replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for personal care decisions.