Your files stay on your device

# Ovulation calculator

Estimate your ovulation day, fertile window, and next periods from your last period date, cycle length, and luteal phase.

Enter the first day of your last period to project the cycle.

This is the textbook calendar model, not a contraceptive method and not a fertility diagnosis. Ovulation is placed at the next period minus the luteal phase, and the fertile window at five days before to one day after; both assume a regular cycle. Irregular cycles, missed ovulation, and cycle-to-cycle variation move the real dates, sometimes by days. Nothing is stored or sent anywhere; this is not medical advice.
Options

## More time & date tools

- [Date calculator](/time/date-math)
- [Duration converter](/time/duration-converter)
[All time & date tools](/time)

Was this tool useful?
YesNo

---

Canonical HTML: https://nutter.tools/time/ovulation-calculator
Markdown version: https://nutter.tools/time/ovulation-calculator.md
Plain-text version: https://nutter.tools/time/ovulation-calculator.txt
Agent index: https://nutter.tools/llms.txt