Pregnancy Calculator: How Many Weeks Am I?
Use this quick calculator to estimate your current pregnancy week, due date, trimester, and days remaining.
Educational use only and not a medical diagnosis. Always confirm timing and care plans with your OB-GYN or midwife.
How this pregnancy week calculator works
Most pregnancy dating is based on gestational age, which starts counting from the first day of your last menstrual period (LMP), not from the day of conception. That means when a test first turns positive, you may already be considered about 4 weeks pregnant.
This calculator estimates:
- How many weeks and days pregnant you are today
- Your estimated due date (40 weeks from LMP, adjusted for cycle length)
- Your current trimester
- An estimated conception date and time remaining
Why doctors count pregnancy from LMP
Clinicians use LMP dating because it gives a standardized starting point. Exact conception timing can be hard to identify, but LMP is often easier to recall and works well for most people with regular cycles.
Early ultrasound can refine this estimate, especially when periods are irregular, ovulation timing varies, or LMP is uncertain.
Understanding your result
Weeks + days format
If your result says 18 weeks and 3 days, it means 18 full weeks have passed and you are 3 days into week 19.
Trimester ranges (general)
- First trimester: weeks 1 to 13
- Second trimester: weeks 14 to 27
- Third trimester: weeks 28 to 40
These ranges can differ slightly by provider, but this framework is commonly used in prenatal care.
Common questions
What if my cycle is not 28 days?
If your cycle is usually longer or shorter, the calculator adjusts the due date. For example, a 32-day cycle can shift ovulation and estimated due date later than a 28-day cycle.
Can this replace an ultrasound?
No. This tool provides an estimate. An early ultrasound is the most accurate way to date pregnancy, especially in the first trimester.
What if I only know my due date?
Select the due-date method in the calculator. It back-calculates your gestational age and an estimated LMP.
Pregnancy milestones by stage
Early weeks (4 to 8)
- Missed period and positive pregnancy test
- Hormonal changes and common symptoms like fatigue or nausea
- First prenatal appointment planning
Middle weeks (13 to 27)
- Energy may improve for many people
- Anatomy scan often completed around week 20
- Steady fetal growth and movement awareness
Late weeks (28 to 40)
- Kick counts and routine prenatal monitoring become important
- Birth planning and hospital bag prep
- Closer follow-up as due date approaches
When to contact your healthcare provider
Seek medical guidance promptly for severe abdominal pain, heavy bleeding, fever, painful urination, persistent vomiting, or decreased fetal movement in later pregnancy. If something feels off, trust your instincts and call your care team.
Final note
If you searched for “pregnancy calculator how many weeks am I,” you’re likely looking for clarity and reassurance. This tool gives a practical estimate you can use right now, but your prenatal provider will give the most accurate timeline for your individual pregnancy.