This due date calculator estimates when your baby is likely to be born using the first day of your last menstrual period (LMP), conception date, ovulation, or IVF transfer date. It applies Naegele’s rule (40 weeks from LMP) or conception-based calculations (38 weeks after conception).
- LMP method: Due date is calculated as 280 days (40 weeks) from the first day of your last menstrual period.
- Conception method: Due date is 266 days (38 weeks) after conception.
- Ovulation method: Due date is estimated from your ovulation day if tracked.
- IVF method: Due date is 38 weeks after embryo transfer.
- Trimester timeline: See when each pregnancy stage begins and ends.
How to use: Enter your LMP date and cycle length, or if known, your conception, ovulation, or IVF transfer date. The calculator will estimate your due date, conception date, pregnancy progress, and trimester breakdown.
Common searches: pregnancy due date calculator, LMP due date calculator, IVF due date estimator, conception to due date, Naegele’s rule calculator.
Due Date Calculator
Estimate your pregnancy due date using LMP, conception date, ovulation, or IVF transfer.
How the due date calculator works
The due date calculator estimates your baby’s arrival using Naegele’s rule and conception-based formulas. With LMP, it counts 280 days (40 weeks) from the first day of your last period. If conception, ovulation, or IVF transfer is known, the calculator counts 266 days (38 weeks) from that date.
Why due dates are estimates
Only about 5% of babies are born on their exact due date. Most arrive within two weeks before or after. Genetics, maternal health, and pregnancy conditions all affect timing. That is why doctors confirm or adjust due dates using ultrasounds and medical assessments.
Trimester breakdown
Pregnancy is divided into three trimesters, each with unique milestones:
| Trimester | Weeks | What happens |
|---|---|---|
| First | 1–13 | Early development, heartbeat appears, major organs begin forming. |
| Second | 14–27 | Baby grows rapidly, mother may feel movement, anatomy scans done. |
| Third | 28–40 | Final growth and maturation, baby prepares for birth. |
Factors that influence due dates
- Cycle length: shorter or longer cycles shift ovulation and conception dates.
- Fertilisation window: sperm can survive up to 5 days, meaning conception may occur days after intercourse.
- Ultrasound scans: often used to adjust due dates based on fetal growth.
- IVF timing: more precise due to known embryo transfer dates.
Limitations of due date calculators
This calculator provides an estimate, not a guarantee. It does not replace medical advice. Every pregnancy is unique, and only a healthcare professional can confirm or adjust due dates accurately.
Due Date Calculator FAQs
A due date calculator gives an estimate. Only about 5% of babies are born on their exact due date. Most arrive within two weeks before or after.
Doctors may adjust due dates after ultrasounds, which measure the baby’s growth more accurately than calendar-based methods.
Full term is between 39 and 40 weeks of pregnancy. Babies born before 37 weeks are considered preterm.
The standard method is to count 280 days (40 weeks) from the first day of the last menstrual period.
Yes. With IVF, the due date is more precise because doctors know the exact embryo transfer date. It is usually 38 weeks after transfer.
Ultrasound in the first trimester is often more accurate than LMP-based calculations, especially for women with irregular cycles.
Yes. If you know your conception date, ovulation date, or IVF transfer date, the calculator can still provide an estimate.