Pregnancy Trimester Calculator
Find your current trimester and weeks pregnant from your last period date.
Your result
Trimesters are counted from the first day of your last period: weeks 1–13, 14–27 and 28–40 onward. Your due date may differ if your cycle was not 28 days.
Medical disclaimer: This tool is for education and is not medical advice. Read more.
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Frequently asked questions
What does the Pregnancy Trimester Calculator do?
Find your current trimester and weeks pregnant from your last period date. Enter your values and the result and chart update instantly.
How accurate is it?
It uses published, widely used formulas. Results are estimates for education and planning, not a diagnosis. Talk to a qualified clinician about decisions affecting your health.
Is my information stored or shared?
No. All calculations run in your browser and nothing you type is sent to a server or saved.
What can I search to find this tool?
People find it by searching for: what trimester am i in; weeks pregnant from period; trimester dates.