Ovulation Calculator
Find your fertile window and likely ovulation day.
Reviewed by Zerunio’s medical team
This estimates your fertile window – the days you're most likely to conceive – from your cycle. It assumes a fairly regular cycle, so treat it as a guide.
This tool gives general estimates for education only – it is not medical advice. Talk to a clinician about your health.
Frequently asked questions
When am I most fertile?
In the five days before ovulation and the day of ovulation itself. Sperm can survive several days, so the days leading up to ovulation matter most.
How is ovulation estimated?
Ovulation is estimated as roughly 14 days before your next period. This tool works it out from your cycle length.
How accurate is this?
It's a guide that assumes a regular cycle. Ovulation predictor kits or tracking your basal body temperature give a more personal picture.
I'm trying to conceive – when should I get help?
See a doctor if you're under 35 and haven't conceived after a year of trying, or after six months if you're 35 or older.