Charting your basal body temperature is a relatively easy and inexpensive way to track ovulation. All you need is an accurate thermometer, a fertility charting app or program (there are lots of free ones available), and some patience.
Overview
While you might think of your temperature as either being normal or feverish, there are a lot of normal variations in between. Our body temperature changes based on movement, how much sleep you’ve had, the time of day, exercise levels, and hormonal changes. After you ovulate, the hormone progesterone begins to rise. Progesterone causes a slight increase in temperature. You can detect this change by charting your basal body temperature. The upward shift caused by ovulation is at least four-tenths of a degree. For example, 98.4 is four-tenths higher than 98.0. If this upward change stays around for at least three days, you can be pretty sure that ovulation occurred on the day before the temperature rise.
Calculating Ovulation
To get pregnant, you need to have sex before the shift occurs. Your chart can help you see when you ovulate each month, so you can time sex for conception better. For the best results, you should also look for other ovulation signs like cervical mucus and mark them on your fertility calendar. If this sounds complicated, don’t worry. Most fertility charting programs do the hard work—like figuring out when you ovulated and when you might ovulate next month—for you. All you have to do is take your temperature correctly and input your information.
Tips
Because the shift you’re looking for is so small, it’s important to take your temperature at the same time every morning before you get up or move. You will need a basal thermometer that displays at least one-tenth of a degree. Just about every thermometer you can buy at the pharmacy does this. Once you’ve got the right kind of thermometer, here’s what to do next: Other factors to keep in mind:
If you need to wake up extra early, or later than usual, take your temperature as you always do. Mark the difference in time on your chart. Yes, it won’t be as accurate, but being one day off isn’t a big deal as long as you’re consistent most of the time.You need to have slept at least four straight hours for your temperature to be accurate. Getting up often at night or have trouble sleeping can throw off your results. You should take your temperature anyway, and note that your sleep was interrupted on your chart.
Charting Your Temperature
Taking your temperature is only part one. You can’t do much with just one basal body temperature reading. You need a consistent series of them, and you need to record them somewhere. One of the most efficient ways to track your basal body temperature is with a fertility charting app or computer program. You won’t have to worry about whether your temperature is sustained long enough or not or spend time calculating when you might be most fertile the next day. The software will do that for you. You can also do your charting by hand on graph paper.
Tracking Cervical Mucus
Another great thing about basal body temperature charting is that you can share your charts with your doctor. If it seems you’re not ovulating, or if your luteal phase looks too short, you can share this information easily with your doctor. The problem with only looking at your basal body temperature is that it only tells you if you ovulated after it happened. But you need to have sex before ovulation to get pregnant. Your basal body temperature can’t warn you that ovulation is coming. Changes in your cervical mucus, however, can. You may see it on your underwear when you wipe after urination, or you can actively check for it by placing a finger into your vagina. Tracking your cervical mucus changes is easy to do, and it is sometimes easier than charting your temperature. Also, most fertility charting apps allow you to put this information into your chart. Your cervical mucus will change throughout your cycle, going from dry and crumbling to creamy, wet, and, finally, to the consistency of raw egg whites. When your vaginal discharge resembles a raw egg white, this is when you’re most fertile and about to ovulate. This is the best time to have sex to conceive. In addition to tracking mucus changes, you can also track changes in your cervical position. This is slightly trickier and has a steeper learning curve, but it may still be worth looking into.
Possible Downsides
Basal body temperature charting is not for everyone. It may not be for you if:
You work night shiftsYou have to get up often in the night with young childrenYou can’t get up at around the same time each dayYou feel stressed needing to track your temperature
Charting may be all the rage on fertility forums, but you can get pregnant without it. You can also try using ovulation predictor tests, or just choose to have sex three to four times a week. At the same time, if you’re using the charting method to try to avoid pregnancy, you need to be diligent and disciplined about keeping at it. You’ll need to also plan to use contraception if you decide to have sex during your fertile days. Lastly, some women won’t see a sustained rise in temperature, even if they do ovulate. If this applies to you, you should mention it to your doctor to determine whether there are other underlying health issues you need to address.
A Word From Verywell
Some women find charting to be an empowering way to learn about their bodies and increase their odds of getting pregnant. The act of taking their temperature and charting may give them a sense of control and confidence with regard to their fertility. For these women, basal body temperature charting is often a positive experience. But if you feel stressed and overwhelmed by charting procedures and results, it may not be for you. The act of timing sex for ovulation (as opposed to having sex frequently and not trying to specifically time intercourse for their fertile window) can add more stress and be a negative experience for some couples. Remember that charting is a choice and there are other fertility tracking options available to you.
