What is BBT Charting?

“BBT” stands for Basal Body Temperature.  This is your temperature when you first awake in the morning. You take it  before you do anything else – use the bathroom, drink coffee, get up, etc.  Throughout a woman’s menstrual cycle, her temperatures follow certain patterns. Charting your temperature is plotting each day’s temperature throughout the cycle.

Why should I chart my BBT?

Charting your BBT will help you to recognize what is going on in your body. It will help you to know if and when you are ovulating, and during which part of the month you are fertile. (This does not always fall at the middle of your cycle, or around day 14, as we are often told.) It can help you achieve or avoid pregnancy by helping you identify this time
frame.

How do I chart my BBT?

There will be a small cost involved in getting started – about $10. You need to buy a BBT thermometer. These are more sensitive than regular fever thermometers, which usually only read to .2 of a degree. (BBT thermometers read to .1 of a degree.)  You should start charting with Day 1 of your cycle.  Cycle Day 1 is the first day of your menstrual flow.  (If you have spotting beforehand, do not count those days; start with the first day of actual blood flow.)

Immediately upon waking, reach for the thermometer and take your temperature.  Try not to move around any more than is necessary, as that will raise your temperature. Make a dot on the appropriate day and temperature on your chart.  (I’ll tell you where to find one later.) It is important that you take your temperature at as close as possible to the same time every morning.  Your temperature rises about .1 of a degree every half hour, so this will otherwise cause your temperatures to appear not to follow their pattern.  If you must take your temperature more than about 20 minutes earlier or later than usual, you can adjust that day’s temperature by adding or subtracting .1 of a degree for each half hour it’s off. If you haven’t been asleep for at least the last 3 hours, your temperature will probably be off. That’s okay, just make sure to make note of it on your chart.

Interpreting Your Chart

At the beginning of your cycle, your temperatures should be in a relatively low range. The day after ovulation you should see a spike in your temperature – it should rise at least .4 of a degree higher than the highest temp. of the past 6 days. (It MAY only rise .2 of a degree the first day after, but continue to rise the following day.) This is due to the progesterone your body produces in order to accommodate a possible new life. Temperatures should stay in this higher range for a while, returning to their lower range around the beginning of your next period. If they remain in this high range for 18 days, you are probably pregnant.

Get My Chart

This is a chart that I designed for myself. It is a Word97 document, and is two pages long. (I print one side, turn the paper over and put it back in, and print the second page on the other side of the same sheet of paper.) The symbols you choose will need to be drawn in by hand after you print it. The first page covers Cycle Days 1-32. 33-45 are on the second page, along with basic cycle information (date, etc.) and the key to symbols.

This chart includes spaces for more information than what I’ve dealt with on this page, so don’t let it confuse you. If you have Microsoft Word, I recommend downloading the .doc file, as you can edit it. If you don’t, you’ll probably need the .pdf file, which requires Adobe’s Acrobat Reader. Chances are, you already have this small, free program.

For more information, I recommend Taking Charge of Your Fertility, by Toni Weschler. It goes into much greater detail than I have here. (It covers some things which many very conservative Christians – myself included – do not agree with. I have not read any other book, however, which covers this topic so thoroughly. Just be aware you will need to filter it as you read. I have heard that The Art of Natural Family Planning is a good one, as well, but have not personally read it.)