Use this pregnancy due date calculator to estimate your baby’s due date, current gestational age, trimester, and important milestone dates.
How this pregnancy date calculator works
A pregnancy date calculator estimates key dates based on your menstrual history. Most tools use Naegele’s rule: add 280 days (40 weeks) to the first day of your last period. Because cycle length can vary, we adjust the estimate by comparing your cycle to a standard 28-day cycle.
For example, if your cycle is usually 32 days, ovulation often happens a few days later than average, so your estimated due date shifts forward slightly. If your cycle is shorter, your estimated due date may shift earlier.
What you get from this calculator
- Estimated due date (EDD)
- Estimated conception date
- Current gestational age in weeks and days
- Current trimester and overall progress
- Important pregnancy milestone dates
Understanding the key dates
Estimated due date (EDD)
Your due date is the projected end of a 40-week pregnancy. Only a small percentage of births happen exactly on this date, so think of it as the center of a delivery window rather than a guaranteed day.
Gestational age
Gestational age is counted from the first day of your LMP, not from conception. That means “2 weeks pregnant” usually occurs before fertilization. This is standard medical dating and helps providers compare fetal growth against established norms.
Trimester breakdown
- First trimester: week 1 to 13
- Second trimester: week 14 to 27
- Third trimester: week 28 to birth
Why your due date can change
Even with a solid pregnancy week calculator, dates may shift as more information becomes available. Early ultrasound measurements are often more accurate than period-based dating, especially if your cycles are irregular or you are unsure of your LMP.
Your clinician may update the due date if scan results and LMP dating differ by a meaningful amount. This is common and usually not a concern.
When to use a pregnancy calculator
A pregnancy due date calculator is useful when you want quick planning information, such as:
- Scheduling your first prenatal appointment
- Estimating when to announce pregnancy
- Planning leave from work
- Tracking symptom patterns by week
- Preparing for trimester-specific tests
Important reminder about medical care
This online tool is for informational use and cannot diagnose complications or replace prenatal care. If you have pain, bleeding, severe nausea, signs of preterm labor, or any urgent concern, contact your healthcare professional immediately.
Frequently asked questions
Is conception date the same as pregnancy start date?
No. Medical pregnancy dating starts at LMP, typically about two weeks before conception in a 28-day cycle.
How accurate is a due date calculator?
It is a strong estimate, especially with a reliable LMP and regular cycles. Accuracy improves with early ultrasound confirmation.
What if I have irregular periods?
Use your best estimate, but expect possible date adjustments at your scan. Irregular ovulation can make LMP-based dating less precise.
Can I rely on this for exact delivery day planning?
No calculator can predict the exact birth day. Use the estimated due date as a planning anchor and stay flexible around the final weeks.