Ovulation Calculator

Enter your last period date and cycle length to predict your ovulation day and fertile window. Plan your conception or track your cycle.

Frequently Asked Questions

How is ovulation day calculated?
Ovulation typically occurs 14 days before your next expected period. For a 28-day cycle, this would be around day 14.
When is the fertile window?
The fertile window spans from 5 days before ovulation to the day of ovulation itself. Sperm can survive in the body for up to 5 days.
How accurate is this calculator?
It is fairly accurate for women with regular cycles. However, it cannot replace medical diagnosis. Use ovulation test kits for more precise confirmation.
Updated 2026 — WHO standards