Pregnancy Due Date & Birth Date Estimator
Choose a method below to estimate your due date, gestational age, and major pregnancy milestones.
How a birth pregnancy calculator works
A birth pregnancy calculator estimates your expected due date by using one of the most common clinical dating inputs: the first day of your last menstrual period (LMP), your conception date, or your IVF transfer date. Most pregnancies are dated to 40 weeks (280 days) from LMP, or about 38 weeks (266 days) from conception.
Because every pregnancy is unique, this tool gives an estimate rather than an exact delivery day. It can still be very useful for planning prenatal appointments, understanding your current trimester, and tracking important milestones.
What this calculator gives you
- Estimated due date (EDD)
- Estimated conception date
- Current gestational age (weeks + days)
- Current trimester
- Typical milestone dates (anatomy scan window, term range, post-term date)
Choosing the best method
1) Last menstrual period (LMP)
This is the standard method in early pregnancy care. If your cycles are regular, LMP dating is usually a good starting point. This calculator also allows cycle-length adjustment for people whose average cycle is shorter or longer than 28 days.
2) Conception date
If you know the day conception likely occurred, the calculator adds 266 days to estimate due date. This is often helpful for people tracking ovulation closely.
3) IVF transfer date
IVF dating can be very accurate because transfer timing is known. The due date depends on transfer day and embryo age (commonly day 3 or day 5 embryo).
Understanding gestational age and trimesters
Gestational age is counted from the pregnancy dating start (roughly two weeks before conception). In clinical practice, this keeps pregnancy timelines consistent for screenings and scans.
- First trimester: up to 13 weeks + 6 days
- Second trimester: 14 weeks to 27 weeks + 6 days
- Third trimester: 28 weeks to birth
Why due dates can change
An estimated due date can shift after ultrasound, especially if cycle dates are uncertain. Your prenatal provider may refine your due date based on fetal measurements in early pregnancy.
- Irregular menstrual cycles
- Uncertain ovulation timing
- Late implantation
- Early ultrasound findings
Important reminder about “due date”
Only a small percentage of babies are born exactly on the due date. Many healthy births happen between 37 and 42 weeks, with most deliveries clustered around weeks 39–40.
Planning tips after using a pregnancy calculator
Book prenatal care early
Schedule your first prenatal appointment as soon as you know you’re pregnant. Early care improves outcomes and helps confirm dating.
Track key milestones
Use the estimated timeline to plan around blood tests, scans, childbirth classes, and parental leave planning.
Discuss your timeline with your clinician
Your healthcare professional can interpret your personal history and confirm the most accurate dating method for your pregnancy.
Frequently asked questions
Is this birth pregnancy calculator medically exact?
No online calculator is a diagnosis tool. It provides a practical estimate. Final clinical dating should come from your prenatal team.
Can I use this if my cycles are irregular?
Yes, but results may be less precise. If your cycles vary significantly, ultrasound dating is often more reliable than calendar-based estimates alone.
Does IVF dating differ from natural conception dating?
Yes. IVF dates can be more specific because transfer timing and embryo age are known, which helps produce a more accurate due date estimate.
Medical disclaimer: This content is for educational purposes only and does not replace professional medical advice, diagnosis, or treatment.