About the Ovulation Calculator
Estimate your ovulation day and fertile window. This tool is free, works in your browser and needs no sign-up.
How to use the Ovulation Calculator
Pick the first day of your last period and enter your usual cycle length. These are estimates only.
Formula used
Ovulation is about 14 days before the next period. The fertile window runs from 5 days before to 1 day after ovulation.
Frequently asked questions
Is the Ovulation Calculator free to use?
Yes. It is completely free and you can use it as many times as you like.
How accurate is the Ovulation Calculator?
The calculator uses standard formulas, so the maths is exact. Real life results can differ because of fees, taxes, rounding or personal factors, so treat the answer as an estimate.
Do you store the numbers I enter?
No. All calculations run in your browser. The values you type are not sent to our server.
Disclaimer: results are estimates for information only. They are not financial, medical or professional advice.