Ovulation Calculator

Estimate ovulation by subtracting the luteal-phase length from your usual cycle length. The period start is cycle day 1. This is educational timing information, not contraception or a guarantee of fertility. Calculate it clearly with Figur.

How the ovulation calculator works

Estimate ovulation by subtracting the luteal-phase length from your usual cycle length. The period start is cycle day 1. This is educational timing information, not contraception or a guarantee of fertility.

Method and assumptions

Figur applies straightforward arithmetic to the values you enter. The calculation runs locally in your browser and is not stored.

  • The result depends on accurate inputs and units.
  • External factors, fees, taxes, or rules not requested by the calculator are not included.
  • Use the result as a planning estimate and verify any high-stakes decision.

Sources and references

No external data source is required: this calculator uses standard arithmetic and the values you enter.

Worked example

A period starts 2025-01-01, with a 28-day cycle and 14-day luteal phase.

Estimated ovulation is January 14, 2025 (cycle day 14).

Frequently asked questions

Can I use this to prevent pregnancy?

No. Ovulation can vary; use a reliable contraceptive method and speak with a clinician for guidance.

What is the fertile window?

Sperm can survive for several days, so conception may be possible in the days before and around ovulation.

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