# Ovulation Calculator

> Ovulation calculator: predict your fertile window and next ovulation date from cycle length and last period. Free, private, runs in your browser, no signup.

- **Canonical URL:** https://boringtoolskit.com/ovulation-calculator/
- **Category:** Everyday Calculators
- **Evidence level:** authored-methodology
- **Reviewed:** August 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

Ovulation ≈ last period + (cycle length − 14) days; fertile window ≈ 5 days before through 1 day after ovulation.

## Sources

- [Calculation methodology and verification standard](/methodology/)

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