How is pregnancy dated?

Pregnancy is counted from the first day of your last period, not from conception, which is why you are already considered two weeks pregnant at conception.

Why do doctors use 40 weeks?

A full-term pregnancy is about 40 weeks from the last period, though anything from 37 to 42 weeks is considered normal.

How Many Weeks Pregnant Am I

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First day of last period

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See exactly how many weeks and days pregnant you are today, which trimester you are in and how long is left. Free.

How to use How Many Weeks Pregnant Am I

Open the toolNo signup and nothing to install; it works as soon as the page loads.
Set “First day of last period”
Read the resultChange any input and the result is recalculated immediately.

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That makes it safe for contract amounts, personal details and internal documents you would rather not hand to a third party — close the tab and it is gone.

What this tool does not do

How Many Weeks Pregnant Am I only does what a browser can do on its own — it talks to no backend service. So it keeps no history for you and syncs nothing across devices; if you need a record, copy or download the result.

It is also not a substitute for professional judgement. For legal, medical or tax decisions, treat the output as a starting point rather than a final answer.

Frequently Asked Questions

How is pregnancy dated?: Pregnancy is counted from the first day of your last period, not from conception, which is why you are already considered two weeks pregnant at conception.
Why do doctors use 40 weeks?: A full-term pregnancy is about 40 weeks from the last period, though anything from 37 to 42 weeks is considered normal.