Ovulation Calculator
NEWEstimate your ovulation date and fertile window.
Frequently asked questions
How is ovulation date calculated?
It predicts your next period (last period start date plus your cycle length), then counts back 14 days — the typical length of the luteal phase (the second half of the cycle, from ovulation to the next period), which stays fairly constant even when overall cycle length varies.
What is the 'fertile window'?
The 6-day span from 5 days before predicted ovulation through 1 day after — reflecting that sperm can survive a few days in the body while the egg is viable for about a day after release, making this the window where conception is most likely.
Can I rely on this for contraception?
No — the tool explicitly notes it's a general estimate based on average cycle patterns, not a reliable contraception method. Actual ovulation timing varies cycle to cycle even for people with regular periods.
Related tools
Calorie Calculator (TDEE)
Calculate daily calorie needs based on weight, height, age and activity.
Water Intake Calculator
Find your daily water intake based on weight and activity.
Sleep Calculator
Calculate the best bedtime or wake-up time based on sleep cycles.
Ideal Weight Calculator
Calculate your ideal body weight using multiple formulas.