Pregnancy Weeks Calculator
Discover your exact gestational age, estimated due date and current trimester.
Calculation Result
You are
Estimated Due Date (EDD):
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Understand Your Result
Naegele's Rule
The calculation adds 280 days (40 weeks) to your LMP to estimate your due date.
Baby Development
Every week brings new changes for you and your baby. Use this calculator as a guide and follow your doctor's recommendations.
Accuracy
Only about 5% of babies are born on the exact due date. Most births happen between 38 and 42 weeks.
Pregnancy Weeks Calculator – How it works
This pregnancy weeks calculator estimates your current gestational age based on the first day of your last menstrual period (LMP) and the average length of your cycle. It also applies Naegele's rule, adjusted for your cycle when necessary, to provide an estimated due date (EDD) and show your progress across the three trimesters.
Why gestational age is counted from the LMP
In clinical practice, gestational age is traditionally counted from the first day of your last menstrual period, not from the date of conception. Ovulation and fertilization are difficult to pinpoint precisely, while the menstrual period is a clear and easily remembered reference. For most people with regular cycles, this method provides a reliable standard for prenatal care and ultrasound scheduling.
Frequently Asked Questions
- 1st trimester: Weeks 1 to 13 (formation of the main organs).
- 2nd trimester: Weeks 14 to 26 (rapid growth and more noticeable movements).
- 3rd trimester: Weeks 27 to 40 (weight gain and preparation for birth).