Introduction
This Ovulation Calculator helps you find the best days to try for a baby. It shows when you are most likely to get pregnant each month.
To use it, pick the first day of your last period on the calendar. Then enter how long your cycle usually lasts. The tool does the rest.
You will see your fertile window, your ovulation day, and the best day to take a pregnancy test. You will also see when your next period may start and a possible due date if you conceive.
The results show up on an easy-to-read calendar and timeline. You can even check up to three cycles ahead, so you can plan with more time.
Not sure how long your cycle is? Use the built-in helper. Just add two period start dates, and it will count the days for you.
These dates are estimates to guide you. Every body is different, so talk to your doctor for advice that fits you.
How to use our Ovulation Calculator
Pick your last period start date and set your cycle details. The calculator shows your fertile window, ovulation day, best test day, next period, and possible due date.
Click the first day of your last period on the calendar. Use the arrows to move between months and tap the day you want.
Choose your average cycle length. This is the number of days from the start of one period to the start of the next. If you are not sure, use the help button to find it.
Set your luteal phase length if you know it. This is the number of days between ovulation and your next period. Leave it at 14 if you are not sure.
Pick how many cycles you want to see. You can view 1, 2, or 3 cycles ahead.
Click Calculate to see your results. Click Reset to start over.
What Is Ovulation?
Ovulation is when one of your ovaries lets go of an egg. This happens about once each month. The egg moves into your tube and waits to meet sperm. If sperm meets the egg, you can get pregnant. If not, the egg breaks down and your period starts about two weeks later.
What Is the Fertile Window?
The fertile window is the best time to try for a baby. It is the few days before ovulation plus the day you ovulate. In the study that first mapped it, conception occurred only with intercourse in the six days ending on the day of ovulation.2 Sperm can live in your body for up to five days, and ACOG says pregnancy is possible from 5 days before ovulation until 1 day after, which is the span this calculator shows.1 So having sex in this window gives the egg and sperm the best chance to meet.
How to Find Your Ovulation Day
To guess your ovulation day, you need two things: the first day of your last period and how long your cycle is. A cycle starts on the first day of one period and ends the day before your next period. The average cycle is 28 days, but yours may be longer or shorter. That is okay.
What Is the Luteal Phase?
The luteal phase is the time from ovulation to your next period. For most people it lasts about 14 days; the standard dating convention assumes ovulation on day 14 of a 28-day cycle.4 This part of your cycle stays about the same length even when your cycle changes. Knowing it helps make your ovulation guess more correct.
The Best Day to Take a Pregnancy Test
The best time to test is the day your period is late. Testing too soon can give a wrong answer. Waiting until your missed period gives a clearer result.
Things to Keep in Mind
These dates are guesses, not exact facts. Stress, sickness, sleep, and other things can change when you ovulate. In a study of 696 cycles, the fertile window fell entirely within days 10 to 17 in only about 30% of women, and on every day from 6 to 21 at least 10% of women were potentially fertile.3 This tool gives you a helpful idea, but it cannot promise a date. If you want sure answers, talk to a doctor or nurse.