Ovulation Calculator
Knowing when you ovulate is key to understanding your fertility. This calculator estimates your ovulation date and most fertile days based on your cycle length and last period date. View predictions for the next 6 months to identify your best chances of conception — or to better understand your body's natural rhythm.
Typical range: 21–45 days (average is 28)
How ovulation calculation works
Ovulation typically occurs about 14 days before the start of your next period. This is because the luteal phase (the time between ovulation and your period) is relatively constant at around 14 days for most women, even when cycle length varies.
Ovulation date: Estimated by subtracting 14 days from your expected next period start date (or equivalently, adding your cycle length minus 14 to your last period start date).
Fertile window: Spans 5 days before ovulation through 1 day after (6 days total). Sperm can survive in the female reproductive tract for up to 5 days, so conception is possible from intercourse that occurs several days before ovulation.
Cycle phases: Your cycle consists of the menstrual phase (your period), the follicular phase (when an egg matures), ovulation (egg release), and the luteal phase (when the uterine lining prepares for possible implantation). The follicular phase length varies with cycle length; the luteal phase is typically fixed at about 14 days.
Fertility Planning
Ovulation predictor kits, basal thermometers, fertility supplements, and tracking tools.
Some links may be affiliate links. If you make a purchase, we may earn a small commission at no extra cost to you.
Frequently Asked Questions
How is ovulation date calculated?
What is the fertile window?
How accurate is an ovulation calculator?
Can I ovulate at different times each cycle?
More Habits Tools
View all →Habit Tracker
Track up to 10 daily habits with a visual streak counter. Build consistency, monitor your longest streaks, and develop healthier routines over time.
Due Date Calculator
Calculate your estimated due date using Naegele's rule based on your last menstrual period or conception date. View your trimester timeline and key pregnancy milestones.
Period Calculator
Predict your next period, fertile window, and ovulation date based on your cycle history. View a 6-month menstrual cycle forecast.
Blood Pressure Checker
Enter your blood pressure reading to see which category it falls into (normal, elevated, or high) based on AHA guidelines, with lifestyle recommendations.
Related Tools
Period Calculator
Predict your next period, fertile window, and ovulation date based on your cycle history. View a 6-month menstrual cycle forecast.
Due Date Calculator
Calculate your estimated due date using Naegele's rule based on your last menstrual period or conception date. View your trimester timeline and key pregnancy milestones.
Stress Reduction Checklist
Work through a science-backed daily stress reduction checklist. Track which stress management techniques you use and build a personalised anti-stress routine.