Starting a Family Ovulation Ovulation Calculator By Wendy Wisner Updated on August 13, 2024 Medically reviewed by Alyssa Dweck, MS, MD, FACOG In This Article View All In This Article How to Use an Ovulation Calculator Best Time to Conceive Ovulation Calculator Accuracy When Does Ovulation Usually Happen? Other Ways to Determine Ovulation Signs of Ovulation Frequently Asked Questions Close When it comes to getting pregnant, it’s all about the timing. Knowing when you're ovulating—and having intercourse on your most fertile days—can increase your chances of conceiving. This is where an ovulation calculator can help. Like ovulation calendars and charts, an ovulation calculator estimates your fertile days based on the length of your menstrual cycle. The difference is that an ovulation calculator does the math for you, providing information about your fertility within seconds. Here, we’ll dive into understanding ovulation calculators, including how they work and how to interpret the results. Then we'll share other tips for optimizing your chances of conceiving. Ovulation happens when an egg is released from one of your ovaries. It typically occurs once during each menstrual cycle—usually about 14 days before your next period begins. But some people ovulate earlier or later than that. How Do I Use an Ovulation Calculator? Using an ovulation calculator is simple and only takes a few short steps. First, you'll be prompted to enter the date of your last menstrual period. It’s fine if you aren't sure of the exact date, but the ovulation calculator result might not be accurate if it's off by more than a day or two. You'll be asked to provide the average length of your menstrual cycle. After you enter this data, the calculator will give you two pieces of information: the predicted ovulation date and the timeframe when you're most fertile. It will also guess when your next period might come. Once your fertile days are determined, you can time intercourse to maximize your chances of conceiving each month. Ovulation calculators work best for people with regular menstrual cycles, but those with irregular periods can try them, too. They're even more effective when paired with other fertility prediction methods, such as monitoring your cervical mucus, taking your basal body temperature, or using ovulation predictor kits. Illustration by Julie Bang. Finding the Best Time to Conceive You should have sex during your fertile window for the best chances of conception. Our ovulation calculator can give you those dates. The fertile window spans about six days during each month—the five days before ovulation, plus the day of ovulation itself. The chances of pregnancy are the highest if you have sex on the three days leading up to ovulation, plus the day of ovulation. "Sperm must be already present and waiting in the reproductive tract for the egg to be released and ovulated. Intercourse must occur before or during ovulation,” explains Arielle Bayer, MD, an infertility specialist and reproductive endocrinologist at CCRM Fertility of New York. Indeed, sperm can survive up to five days in the reproductive tract, while an egg lives for about 12 to 24 hours after ovulation. That means days-old sperm can fertilize a newly released egg, which can result in pregnancy. How Often to Have TTC Sex Many people want to know if it’s necessary to have sex every day when you're trying to conceive, or if spacing it out is better. You should do whatever works for you, but some experts recommend waiting a day or two between intercourse sessions to maximize sperm production. “The sperm samples are typically better when the male partner has had two to five days of abstinence between ejaculations,” says Dr. Bayer. “So, I tell my patients that sex every other day leading up to ovulation is ideal (and often less pressure)!” How Accurate Are Ovulation Calculators? Ovulation calculators are only estimates. They can’t guarantee accurate information, because menstrual cycle length and ovulation timing can vary, even from month to month. Still, for certain individuals, ovulation calculators can be quite precise. It's "most accurate for women who have regular cycles,” says Caroline Skahn, CNM, certified nurse midwife with UTHealth Houston. This means the length of your menstrual cycle is the same each month. For people with irregular or unpredictable cycles, ovulation calculators may be less likely to pinpoint the exact fertile window, since ovulation times often vary, says Jill Purdie, MD, a board-certified OB-GYN and medical director at Pediatrix Medical Group in Atlanta. Still, they can provide a general guideline for when ovulation is most likely to occur. When Does Ovulation Usually Happen? Most people with a regular menstrual cycle ovulate roughly halfway through it, says Caroline Skahn, CNM, certified nurse midwife with UTHealth Houston. During a typical 28-day cycle, ovulation occurs about 14 days into the cycle. What if you don't have a 28-day cycle? The general guideline is 14 days before your next period starts, no matter your cycle length, according to the American College of Obstetricians and Gynecologists (ACOG). If your cycle is 35 days long, for instance, you'll probably ovulate on day 21. If your cycle is 24 days, you'll ovulate around day 10. Can I Only Get Pregnant During Ovulation? Yes, you can only get pregnant around the time of ovulation. If you miss your fertile window and your ovulation day, you'll need to wait until the following month before trying to conceive again. No worries—it will be here before you know it! Chances of Pregnancy Each Month Determining your fertile window can increase your chances of pregnancy success, but keep in mind that even when everything goes right, it can take several tries to conceive. According to ACOG, healthy couples in their 20s and early 30s have about a 25% chance of getting pregnant in any given cycle. After the age of 40, your chances of conceiving drop to about 10% per cycle. Other Ways to Determine Ovulation There are several other ways to determine ovulation, and you can combine them with an ovulation calculator to maximize your chances of conceiving. Here’s what to know about these methods. Cervical Mucus Changes Your cervical mucus looks different throughout your cycle. Around the time of ovulation, it tends to be more abundant, stretchy, clear, and slippery, with an appearance and consistency like raw egg whites. This means that you are likely fertile. Basal Body Temperature Measuring and charting your basal body temperature (BBT) can help you conceive, says Dr. Purdie. “With this method, a patient takes their temperature every morning prior to getting out of bed,” she describes. You have to use a special thermometer called a basal body thermometer. Each time you take your temperature, you record it on a chart. You've likely ovulated when you notice an increase of 0.5–1°F. The BBT method “can help one confirm that they've already ovulated (by the rise in temperature which occurs after ovulation) but will not be helpful to predict when ovulation is about to occur,” says Dr. Bayer. Ovulation Predictor Kits Ovulation predictor kits (OPKs) look for the hormone released to trigger ovulation (luteinizing hormone or LH). You will get a positive test result on these kits about 36 hours before you actually ovulate, says Dr. Purdie. “These methods can confirm what the patient is seeing on their calendar as the ovulation date,” she explains. OPKs can be helpful for people with irregular periods looking to better predict ovulation. Signs of Ovulation Some people notice signs of ovulation in the body. It might be helpful to record them for a few months so that you can see a pattern and better understand your body's response. You might even use these signs of ovulation, along with ovulation calculators and the other prediction methods described above, to time intercourse when trying to conceive. The signs and symptoms of ovulation may include: Mild cramping on one side of the pelvis Increased, slippery cervical fluid Heightened sex drive Mood changes, including increased energy Breast tenderness Frequently Asked Questions How soon should you take a pregnancy test after ovulation? Most health care providers recommend waiting until the day after your expected period to take a pregnancy test. This is usually about two weeks after ovulation. Are there medical conditions that can affect ovulation? Medical conditions that can affect ovulation include polycystic ovarian syndrome (PCOS), thyroid issues, hormonal imbalances, primary ovarian insufficiency (POI), and more. Certain lifestyle and environmental factors can also affect ovulation, such as high levels of stress, drug use, and excessive physical activity. How long should I try to conceive before seeking medical advice? For people under the age of 35, most providers recommend seeking fertility advice after one year of trying. However, if you're over the age of 35, you should get a fertility workup after six months of trying. Those over 40 should see a fertility specialist before trying to conceive. Can birth control affect ovulation after discontinuation? Some people start ovulating right away after stopping hormonal birth control, but for others, it can take a few cycles to start ovulating again. Reach out to your health care provider if you have further questions about trying to conceive after stopping birth control. When should I have sex? “You should have intercourse in the third, second, or first day before expected ovulation,” suggests Dr. Bayer. “Intercourse on the exact day of ovulation is good, too.” Remember, sperm can live up to five days in your reproductive tract, so it’s a great idea to have sex before the egg releases so that some sperm are ready and waiting. Was this page helpful? Thanks for your feedback! Tell us why! Other Submit Sources Parents uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Trying to Get Pregnant? Here’s When to Have Sex. American College of Obstetricians and Gynecologists. 2022. Your menstrual cycle. Office on Women's Health. U.S. Department of Health and Human Services. Updated 2021. Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy. American College of Obstetricians and Gynecologists. Updated 2023. Cervical Mucus Monitoring. UNC School of Medicine. Fertility Awareness-Based Methods of Family Planning. American College of Obstetricians and Gynecologists. Reviewed 2022. Ovulation home test. MedlinePlus [Internet]. National Library of Medicine. Reviewed 2023. What are some possible causes of female infertility? Eunice Kennedy Shriver National Institute of Child Health and Human Development. National Institutes of Health. Reviewed 2017. What lifestyle and environmental factors may be involved with infertility in females and males? Eunice Kennedy Shriver National Institute of Child Health and Human Development. National Institutes of Health. Reviewed 2022. Infertility FAQs. Centers for Disease Control and Prevention. Reviewed 2023. When will my periods come back after I stop taking the pill? United Kingdom National Health Service. Reviewed 2022.