# Estimated ovulation window

Canonical page: https://nepocore.com/tools/ovulation-window/

Explore an approximate ovulation interval from an assumed regular cycle. 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

For a 28-day cycle, compare estimated ovulation with the predicted next period.

## Limits and checks

Timing varies, especially with irregular cycles. These dates cannot confirm ovulation and must not be used as reliable contraception.

## 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 — fertility in the menstrual cycle](https://www.nhs.uk/conditions/periods/fertility-in-the-menstrual-cycle/)
- [NHS — fertility-awareness limitations](https://www.nhs.uk/contraception/methods-of-contraception/natural-family-planning/)

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