Pregnancy Week Calculator
Choose one method below to estimate how many weeks pregnant you are today.
How this “how many weeks pregnant” calculator works
This tool estimates gestational age, which is the standard way pregnancy is measured in weeks and days. In most clinics, pregnancy dating starts from the first day of your last menstrual period (LMP), not from conception day. That means you are typically considered about 2 weeks pregnant at the time of conception.
Our calculator gives you a quick estimate of:
- Your current pregnancy age in weeks + days
- Estimated due date
- Current trimester
- Time remaining until 40 weeks
Why dates can vary slightly
Pregnancy dating is an estimate. Even with regular cycles, ovulation can shift by a few days. That is why ultrasound measurements in early pregnancy are often used to confirm or adjust the due date.
Common reasons your estimate may differ from your doctor’s date
- Irregular menstrual cycles
- Uncertain LMP date
- Late or early ovulation
- Early ultrasound recalculation
How to use each method
1) Using LMP (most common)
Enter the first day of your last period and your average cycle length. This method is standard and works well for many people, especially if cycles are somewhat predictable.
2) Using an estimated due date
If your provider already gave you a due date, choose the due date method. The calculator counts backward from 40 weeks to estimate your current pregnancy week.
3) Using conception date
If you know roughly when conception occurred, this method adds 14 days to estimate gestational age, because medical pregnancy dating includes the approximately two weeks before ovulation.
Understanding your result
If your result says 18 weeks and 3 days, that means you are in the 19th week of pregnancy. Week counts can feel confusing at first, but this format is what most prenatal records use.
- First trimester: 0 weeks to 13 weeks 6 days
- Second trimester: 14 weeks to 27 weeks 6 days
- Third trimester: 28 weeks onward
Frequently asked questions
How many weeks pregnant am I if I just got a positive test?
Many people are around 4 to 5 weeks pregnant at the time of a first positive home test, depending on cycle timing. Enter your LMP for a more personalized estimate.
Can this replace an ultrasound?
No. This calculator is for educational use and quick estimation. Ultrasound and professional prenatal care are the most accurate ways to confirm dating and monitor pregnancy health.
What if I don’t remember my exact LMP?
Use the due date or conception method if you have that information. If dates are uncertain, your prenatal provider can help establish the best estimated gestational age.