# Pregnancy week & trimester

Canonical page: https://nepocore.com/tools/pregnancy-weeks/

Calculate weeks, days and trimester from an entered pregnancy reference date. This browser tool shows the inputs, assumptions and resulting output so you can use it for a specific everyday task.

## How to use it

1. Enter your own values or choose a supported file.
2. Adjust the options and run the tool.
3. Review the result, then copy, export or save it when available.

## Example

Enter the last-period date and a reference date to see elapsed weeks and days.

## Limits and checks

LMP dating assumes an appropriate reference date. A clinician may adjust pregnancy dating; use their confirmed date for care.

## Access and processing

Free to use without an account. Interactive processing requires JavaScript in a modern browser. Input is processed in the browser rather than sent to a processing server. Optional browser storage is not a synchronized account.

## Method and sources

- [NHS — estimated due date and dating scans](https://www.nhs.uk/pregnancy/finding-out/due-date-calculator/)
- [ACOG — fetal development and trimesters](https://www.acog.org/womens-health/faqs/how-your-fetus-grows-during-pregnancy)

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