Pregnancy Week Calculator
See how many weeks pregnant you are, your trimester and key milestones.
Enter your values to see the result.
These results are estimates for general information, not medical advice. Body shape, muscle mass, age, ethnicity and health conditions all affect what is right for you, so talk to a doctor or dietitian before making health decisions.
Continue your work
- Due Date Calculator — Calculate the due date.
- Ovulation Calculator — Track fertile days.
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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
How to use the Pregnancy Week Calculator
See how many weeks pregnant you are, your trimester and key milestones.
- 1 Choose what to calculate from and enter the date.
- 2 Read how far along you are, your trimester and progress.
- 3 Check the milestone dates in the table.
Example and practical tips
Seventeen weeks after the last period you are in the second trimester, and the baby is about the size of a sweet potato.
Frequently asked questions
When do pregnancy weeks start?
From the first day of the last period, about two weeks before conception.
When are the trimesters?
The first runs to the end of week 13, the second to the end of week 27, and the third until birth.
Report an issue
Something broken or not quite right? Tell us and we will look into it.