How to Chart Your Menstrual Cycle

Medically Reviewed by Carol DerSarkissian, MD on February 20, 2022
3 min read

Getting pregnant is all about timing. You want to make sure the conditions are right for egg and sperm to meet. Your menstrual cycle can give you clues about when your body is ready to start the process.

The first step is to learn the days when you're most fertile. Most women have a 28-day menstrual cycle. That means you have about 6 days each month when you can get pregnant. That includes the day that one of your ovaries releases an egg, called ovulation, and the 5 days before. Having sex within that window is key. You can’t get pregnant without ovulation, and tracking your monthly periods is one way to get familiar with your body’s fertility.

To figure it out, you'll need to chart your menstrual cycle and record how long it lasts. Day 1 is the first day of your period. Since the length of your cycle can vary slightly from month to month, it's best to keep track for a few months.

Once you have an average, subtract 18 days from the length of your shortest cycle. This is the first day you're likely to be fertile. Next, subtract 11 days from the length of your longest cycle. This is the last day you're likely to be fertile. Having sex between those two dates will give you the best shot at getting pregnant.

It's also a good idea to pay attention to the signs that your body is ready to ovulate. Checking your basal body temperature (BBT) is one way to do this.

The BBT is your temperature first thing in the morning. Just after you ovulate, it rises slightly -- sometimes by less than a degree -- and stays higher until your period starts. If you record your temperature every day, you can spot the subtle changes that mean one of your ovaries has released an egg.

To take your BBT, you need to:

Use a basal body thermometer. It's more sensitive than a standard one and will show temperature changes down to a fraction of a degree. You can get them at many pharmacies for less than $20.

Take your temperature at the same time each morning. Always do it before you get out of bed. (To make it easier, keep the thermometer on your nightstand.) Even getting up to go to the bathroom can affect your body temperature. So can smoking, drinking, or getting a bad night's sleep.

Remember, your BBT won't tell you exactly when you've ovulated, and it may take a couple of months before you start to see a pattern. You're most likely to get pregnant 2 or 3 days before your ovary releases an egg, and then another 12 to 24 hours after that. When your temperature has spiked for 3 days, your chances of conceiving drop.

The same hormones that control your menstrual cycle also affect the mucus that your cervix makes. Just before and during ovulation, the amount, color, and texture of it change to make it easier for you to get pregnant.

As your ovaries prepare to release an egg, your cervix makes more mucus. A few days before ovulation, it may be sticky and cloudy or whitish. Then, right before you ovulate, the mucus gets slippery, like egg whites. It may stretch across your fingers if you spread them apart. This stage usually lasts 3 or 4 days, which is when you're most likely to get pregnant.

To check your cervical mucus:

  • Use your fingers or a tissue to check the opening of your vagina for mucus a few times a day. Make sure your hands are clean before you start. Write down whether it's cloudy and sticky or clear and slippery.
  • Chart your cervical mucus changes and your basal body temperature to get a clear picture of where you are in your cycle.

Keep in mind that other things, like breastfeeding, can change your mucus. Using douches or other hygiene products can also affect it. Gynecologists usually don't recommend these products.