Charting your BBTs is really pretty easy. Basically, what you are doing is taking your temperature first thing each day and plotting the temperature on a chart. What you are looking for is to see a shift of at least .4 degrees Fahrenheit after ovulation making your chart biphasic (showing low temperatures before ovulation in the follicular phase, and higher ones after ovulation in the luteal phase). Be sure to use ovulation tests in conjunction with your basal charting to provide you with an accurate sense of your most fertile time of month. For a 5-7 day advanced notice of ovulation, consider using an electrolyte-based fertility tracker.
Take your temperature first thing in the morning before you get out of bed or even speak — leave your thermometer at your bedside within easy reach so you don’t have to move much to get it. If you use a glass thermometer, make sure you shake it down before going to bed.
Try to take the temperature at as close to the same time each day as possible — set an alarm if you need to. Staying within a half hour either side of your average time is a good idea because your temp can vary with the time (i.e., if you usually take your temperature at 6 a.m., it is OK to take your BBT between 5:30-6:30, but the closer to 6 the better). The normal variation is by up to .2 degrees per hour — lower if you take your temperature early, higher if you take it late.
It is best to take your BBT after a minimum of 5 hours sleep, and at least 3 in a row is preferable.
You can take your temperature orally, vaginally, or rectally — just stay with the same method for the entire cycle.
You should try to place the thermometer the same way each day (same location of your mouth, same depth vaginally and rectally).
Plot your temperature on your chart each day, but refrain from reading too much into it until the cycle is done.
Some women, not all, have a temperature drop when they ovulate. If you see this drop, it is a good idea to have sex in case you are ovulating.
What you are looking for is a temperature shift of at least .4 degrees over a 48-hour period to indicate ovulation. This shift should be above the highest temperatures in the previous six days, allowing one temperature to be thrown out as inaccurate (fluke, illness). Perhaps the best way to explain this is to show an example:
In the image above, the seven BBTs before ovulation are 97.2, 97.3, 97.8, 97.4, 97.2, 97.3, 97.0 then it jumps to 97.7 and then 98. Ovulation most likely occurred on the day with the 97.0 and you can comfortably draw a coverline at 97.6. You just ignore the 97.8 on day 10.
9. After you see a temperature shift for at least three days, or at the end of your cycle, you can draw a coverline between your follicular phase and luteal phase temperatures. With luck, it is easy to see a clear shift and draw your line between the highest follicular phase BBT and the lowest luteal phase BBT as in the sample above. The main reason for drawing this line is just to clearly delineate that your chart is biphasic.
10. Look at the chart at the end of the month to analyze what happened.
11. Chart for a few months and look for patterns.
12. If your temperature stays up for 18 days or more after ovulation, you should test for pregnancy.
One thing to note is that women with ovulatory cycles but with irregular cycle lengths, the greatest variation from cycle to cycle should be in the follicular phase. The luteal phase should be relatively constant (within 1-2 days). So if one has a cycle that ranges from 28-34 days, and a luteal phase of 14 days, ovulation would occur somewhere between days 14-20 — not the middle of a cycle, not day 14 . . . This is the biggest mistake women with long cycles make when trying to conceive.
Charting Cervical Mucus and Cervical Position
If you want a clearer picture of your cycle, it is best to combine charting your BBT with charting your cervical mucus (CM) and perhaps also charting your cervical position.
There are several ways to chart your mucus, and you have to find the approach that is best for you. You can simply examine your toilet tissue after wiping. You will see more mucus after you have a bowel movement. Another way is to insert two fingers and gently take a little pinch of mucus from the cervix.
The easiest positions for most women would be sitting on the toilet, one foot up on the toilet or bathtub, or squatting. If you have trouble reaching, you can ask your partner to check for you. For most, the best position to do this would be for the woman to get on all fours on the bed, or chest down on a pillow, and let the partner insert fingers from behind. Otherwise your partner will be crawling around on the floor!
Cervical Mucus
Mucus varies from dry, to sticky, to creamy, to egg-white (EW) before ovulation in most women.
Dry is when there really isn’t much mucus to get your fingers on.
Sticky is when you get enough mucus for your fingers to feel sticky or tacky.
Creamy might be whitish and feels somewhat like lotion when you rub your fingers together. This mucus can be fertile, but isn’t always.
Egg-white cervical mucus (EWCM) is called that because of its resemblance to raw egg whites. It is either clear or streaked and stretches an inch or more. Sometimes it is watery. FertileCM can help to produce more EWCM.
After ovulation it is normal to have some dry, sticky or creamy mucus, and some women have watery mucus or a little egg-white again right before their menses begins.
Cervical Position
If you are planning to chart cervical position in addition to BBTs and mucus, it makes sense to chart your mucus by feeling your cervix (or having your partner do it).
You cervix has a pattern each month . . . it should start out low, closed and firm. Around ovulation it shifts upward, gets softer and feels more open. The difference is slight — like the difference between feeling your nose (firm) and feeling your lips (soft). It should only stay high for a day or two around ovulation and you may catch it in transition for a day on either side. The rest of the luteal phase (after ovulation) the cervix should be low. It is often soft right before menses. It tends to shift up if you are pregnant.
One caution is that you shouldn’t read too much into cervical position alone since how full your bowels are can make a difference as to how high it feels.