# Ovulation Calculator | Clever Mum

> Estimate your fertile window and likely ovulation day from your cycle dates — and understand what the estimate can and can’t tell you.

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# Ovulation Calculator

    
 
Quick answer — How does the ovulation calculator work? 

 
Ovulation typically happens about 14 days before your next period starts. Enter your last period date and cycle length to estimate your fertile window — the five days before ovulation plus ovulation day itself. Calendar estimates are a guide, not a guarantee.

     First day of your last periodAverage cycle length: 28 days
Calendar estimates assume ovulation ~14 days before your next period, which varies between people and cycles. For accuracy, combine with ovulation tests or cervical-mucus tracking. If cycles are irregular or you've been trying for over a year (or 6 months over 35), talk to your GP. General information, not medical advice.

      
Trying to conceive?

 

Our [trying to conceive guide](/pregnancy/trying-to-conceive-improving-your-chances/) 
covers timing, preparation and when to see a GP, and our  [how long does it take](/pregnancy/how-long-does-it-take-to-get-pregnant/) 
article has the realistic statistics if you're feeling anxious about the wait.