How do I Calculate my Ovulation Cycle?

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  • Originally Written By: Jessica Saras
  • Revised By: C. Mitchell
  • Edited By: Michelle Arevalo
  • Last Modified Date: 09 December 2018
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There are a couple of different ways to calculate your ovulation cycle, but three of the most common are the calendar method, the body temperature method, and the cervical mucus method. All of these require you to keep track of your periods and pay attention to little changes in your body each day, and often take a few months to start getting good results. It’s also possible to buy commercial ovulation calculators or tests in some markets. None of these methods are foolproof, though. Each woman’s cycle is different, and calculating the precise moment of ovulation is often more of an educated guess even for those with extensive training in reproductive health.

Ovulation Basics

In healthy women, ovulation happens once a month when the ovaries release an egg into the uterus for fertilization and implantation. Although the actual egg release happens at one precise time, women are typically considered “fertile” for a couple of days on either side. Pregnancy is much more likely during this span, which makes calculating your ovulation cycle really important both if you are trying to get pregnant and if you are trying to avoid pregnancy. Eggs that are not fertilized disintegrate into the uterine lining and are flushed out of the body during the menstrual period, and there isn’t another chance for a baby until the next month.


Length of Menstrual Cycle

The so-called “calendar method” is one of the most popular ways to calculate your likely window of ovulation, and it depends on counting out the days of your menstrual cycle to make an educated guess about when your eggs are released. Most women have cycles of between 28 and 30 days, but you will need to count yours out to get the most accurate results. Start with the last day of your period, then tally up the full days until the next cycle starts.

It’s usually a good idea to calculate the length of your cycle for two to three months to determine an average number since things can vary a little bit over time. A certain degree of precision is required, though. If the length of your cycle varies by more than a few days each month, you may want to talk with a doctor to come up with a more accurate method.

Luteal Phase Calculation

Once you know your average length, you will need to determine the length of your luteal phase, or days past ovulation (DPO). This is basically the number of days in your cycle after the egg drops but before you start your period. These two numbers together will give you a good idea of when you’re ovulating. Although blood tests are the only way to determine the exact length of your luteal phase, 14 days is the average for most women. As a result, it’s usually safe to assume a 14-day phase if you don’t have a more accurate number.

Next, subtract the length of your luteal phase from the total length of your cycle to predict when ovulation will occur. For example, if your menstrual cycle lasts 30 days and your luteal phase is 14, your ovulation cycle will begin on the 16th day of your cycle (because 30 minus 14 is 16). Although an egg will only be available for about 24 hours, sperm can survive for three to five days. Therefore, your most fertile time will be about two to three days prior to and after your ovulation cycle begins. To increase your chances of becoming pregnant, you should plan to have intercourse approximately two days before you ovulate and again on the day of ovulation; to avoid pregnancy, avoid intercourse during these times.

Basal Temperature Method

Your temperature will also go up slightly during ovulation and you may be able to pinpoint the exact day and time of your egg release by monitoring these statistics, too. Temperature fluctuations are usually very subtle which means you will probably need a very precise thermometer if you want to use this method. Most experts recommend getting a measurement first thing in the morning, usually before you have even gotten out of bed. This “resting” temperature is known as the “Basal temperature,” and is widely believed to be the most precise.

Over the span of several months, take your temperature right when you rise, at about the same time each day if possible. Record your measurements and, after a few months, look back at everything together. Under ideal circumstances, your temperature should be basically the same every day but for one or two subtle spikes somewhere mid-month. This is when you are ovulating. You can use this data to identify when you are likely to ovulate in the future. It is important to realize that sickness, medications, and alcohol can all have an impact on temperature, which can make this method somewhat imprecise.

Tracking Cervical Mucus

Your cervix, the opening to the uterus, is coated in mucus that changes in both thickness and texture as your body prepares for ovulation and menstruation, and though the distinctions are subtle many women do have success tracking them as a way of making a precise calculation. Like with your temperature, this method tends to work best when you have a few months’ worth of data to work with.

You should start by choosing a single time each day for your check. Insert one or two fingers into your vaginal opening to feel for any mucus secretions, and then write down notes about their consistency and color. Over time you should notice one or two days each month where your mucus is particularly clear, stretchy, and highly slippery; this is when you are ovulating. Again, certain environmental factors can impact mucus texture and feel, so this method is not foolproof; with practice, though, it can give fairly accurate results.

Commercial Tests

Pharmacies and fertility health clinics sometimes offer patients specialized ovulation tools or tests, most of which work by testing urine for elevated hormone levels. Some include data tracking and information storage to hold information over a span of several weeks or months to give the most accurate, personalized results possible. These tend to be somewhat costly, and they usually have to be used very precisely.

Special Circumstances

If you have reproductive health problems, including uterine fibroids or cysts, you may not have good luck with any of these methods since your ovulation might be irregular. Certain medications and therapeutic treatments like radiation or chemotherapy also tend to alter ovulation patterns, sometimes permanently. Women who are seriously overweight or underweight may also experience irregular cycles that can make ovulation tracking tricky if not impossible. If you are concerned about the regularity of your cycle, it’s usually best to talk to a healthcare professional who can help you come up with a personalized calculation plan.


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Discuss this Article

Post 14

I am 42 years old and have a daughter who is 14 years old. I had an abortion twice last year. Now I want to have a child. Will my health support it, and what do I have to do?

Post 13

I had surgery for fibroids four months ago, and since then I've been following the doctor's advice, but still haven't gotten pregnant.

Also, my periods have become irregular after almost three months, and clotted, so please suggest to me how I can get pregnant. On which dates should I have sex with my husband? Please do help me so that I will be a mother as soon as possible.

I have been trying to get pregnant for almost two years now. I don't have a regular cycle. How will I know when I am fertile? What do I do now?

Post 12

If my period date is on the 23rd, how can I get pregnant with a boy?

Post 10

My last menstruation was late June. When do I ovulate?

Post 9

If you're seriously overweight, speak to your doctor about starting a gradual weight-loss program. Obesity may affect hormonal signals to the ovaries and interfere with ovulation.

Post 8

@anon327984: The male determines the sex of the child. A woman releases an egg that carries an X chromosome. If the man's sperm cell that fertilizes the egg has an X chromosome, the baby will be a girl. If the sperm cell carries a Y chromosome, the child will be a boy. Some couples have opted for sex-specific in vitro fertilization, but this is an expensive procedure, and only a fertility doctor can do it. Otherwise, there isn't much you can do, except make sure you're healthy and get good prenatal care.

Post 7

I am a mother of three girls and am 42 years old. I want to get pregnant again. How can I calculate my body temperature so that I can deliver a baby boy?

Post 6

@anon309836: You need to ask your OB doc about your probable date range for conception. He or she can give you a window, based on your due date and the date of your last period, which should give you a better idea.

Post 5

I am a bit worried because I'm not sure if my boyfriend is the father of my baby. I hope he is. The date of my last period was three days after we started going out. We had sex that day but he had pulled out. I'm not sure if he started ejaculating inside me like a week or two weeks after my period. I am now 19 weeks. Could this be his baby?

Post 4

I had surgery for a chocolate cyst 6 months ago, and since then I've been following the doctor's advice, but still haven't gotten pregnant.

Also, my periods have become irregular and after almost two months, I finally had one, so please suggest how I can get pregnant. On which dates should I have sex with my husband? Please do help me so that I will be a mother as soon as possible.

Post 3

I have been trying to get pregnant for almost two years now. I don't have a regular cycle. How will I know when I am fertile? I have also tried to have a transvaginal ultrasound, and it shows that I have polycystic ovaries. What do I do now? --MrsFierced

Post 2

@MrsWinslow - Well, if you have sex every other day, or every day, then you'll know you won't miss your window!

But I get what you're saying. The kits do work. I had been trying to get pregnant for a long time and got pregnant the first month I used one! The only problem is that it's not that different from the temperature shift. When your temp. goes up, it's already too late; when you get a positive on the ovulation predictor kit, it's almost too late. The best day to have sex is the day before the temp. shift!

It's one more thing that's worth trying. Another way to find out more about your ovulation cycle and fertility is to check the position of your cervix--that will give you longer warning that ovulation is coming than the OPK. If you haven't taken a class or read a whole book on FAM, you really should; there's a lot of good info.

Post 1

What about ovulation predictor kits? Do they really work? I'm trying to get pregnant but I want to stay out of my doctor's office as much as possible. I'd rather pee in a cup at home than have my doctor draw my blood!

I've been told about the Fertility Awareness Method, which involves taking your body temperature every day to see when you ovulate, but I'm interested in the kits as an adjunct to that. My cycle is different every month and I can't tell from my cervical fluid when I'm going to ovulate--once my temperature goes up, I know it's too late.

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