Pregnancy Due Date & Timeline Calculator
Use this calculator to estimate your due date, current gestational age, trimester, and important milestones.
This tool is for education only and does not replace professional medical advice, diagnosis, or ultrasound-based dating.
What this pregnancy calculator does
A pregnancy calculator helps estimate your due date and your current gestational age (how many weeks and days pregnant you are). It can also outline key timeline milestones, such as when each trimester begins and when you reach full term.
This calculator supports three common methods:
- LMP method: based on the first day of your last period.
- Conception date method: useful when conception timing is known.
- IVF method: based on embryo transfer date and embryo age.
How pregnancy dating works
Gestational age vs. fetal age
In obstetrics, pregnancy is usually dated from the first day of the last menstrual period (LMP), not from conception day. That means gestational age is typically about 2 weeks more than fetal age.
Why 40 weeks is the standard
A full pregnancy is often estimated as 280 days (40 weeks) from LMP. If your cycles are longer or shorter than 28 days, your estimated due date may shift accordingly.
Due date is an estimate
Only a small percentage of babies are born on the exact due date. Many healthy births occur before or after that day. Your clinician may revise dating based on ultrasound findings, especially in early pregnancy.
When to use each method
1) Last menstrual period (LMP)
Use this if you know the first day of your last period. This is the most commonly used method in early pregnancy tools.
2) Conception date
Use this if conception timing is known with reasonable confidence (for example, tracked ovulation and timing).
3) IVF transfer
IVF dating is often more precise because transfer date and embryo age are known. This tool uses those values to estimate gestational age and due date accordingly.
Important pregnancy timeline milestones
- End of first trimester: around 13 weeks 6 days
- Start of third trimester: 28 weeks 0 days
- Early term: 37 weeks 0 days
- Full term: 39 weeks 0 days
- Estimated due date: 40 weeks 0 days
These are general reference points. Clinical care should always be individualized by your healthcare team.
How to use your results wisely
Use it for planning, not diagnosis
The calculator can help with practical planning (appointments, leave timing, baby prep), but it is not a medical diagnosis.
Confirm with prenatal care
Your provider may confirm or adjust dates using ultrasound, cycle history, and clinical context.
Track trends over time
Re-checking timeline milestones can make it easier to stay organized throughout prenatal visits and trimester transitions.
Frequently asked questions
What if I have irregular cycles?
The LMP method can be less accurate with irregular cycles. If you know conception date or IVF details, those methods may be more reliable.
Can this replace an ultrasound due date?
No. In many cases, early ultrasound is the most accurate way to confirm gestational dating.
What if the due date has already passed?
The calculator will still show the timeline and indicate that the estimated due date is in the past.
Safety note
If you have pain, bleeding, severe symptoms, or any urgent concern, contact your healthcare provider or emergency services right away. Online tools are informational only and cannot evaluate emergencies.