The CCL STM Chart Over the Years


Written by Stacey Nagle, Elizabeth Timpe and Bernadette Jones. Originally published in Family Foundations.


Have you ever tried to create your own chart? Perhaps you tried a spreadsheet or other alternative chart and experimented with other ways to input temperatures and add mucus observations. Or perhaps you had always thought about making your own but never got around to it. Over the years, the CCL chart has had just a few different looks. In this article, we will take a look at the same cycle charted on paper charts and on the new PeakDay app.

Chart 1 Paper Chart (1986)

The earliest chart is from one with a copyright of 1986. The original CCL paper chart is a gem! It has a place for everything needed to evaluate your cycle and keep track of cycle variations. It also has large boxes that made for some interpretation on where to put each temperature. If it was an even temp (97.8), no problem, right on the line. Odd temperature (97.9) needed to be placed in the middle of the box. Middle school children graph on paper like this! As you can see from the early chart, that didn’t always happen. The person charting did not sometimes get the mark on the line! There were also multiple mucus symbols for feelings or sensations, as well as “qualities you can see,” plus “other mucus symbols”. So much to keep track of! The front of the chart booklet listed all of the chart interpretation rules for the end of phase I and the start of phase III. Using Rule R, the start of phase 3 was day 23.


Chart 2 Paper Chart (2007)

In 2007, the chart was updated to match the new STM rule. The boxes for temperatures were replaced with numbers to color over for the temperature to lessen any confusion to the actual number. The Peak day row was moved to directly under the temperatures to ease the interpretation for phase 3. The new chart added the symbols row so that each day the mucus sign could be evaluated and marked. The mucus observations were also simplified to two categories, sensations and characteristics, and the cervix observation remained in the same spot on the chart as before. This chart booklet also utilized both sides of the paper giving you twice as many charts! Chart number, Date and History were added to the side instead of the top of the page, but was still nicely organized. This chart booklet is so easy to use that it’s one of CCL’s best sellers. The same 1986 cycle is recorded on this 2007 type chart. Using the Sympto-Thermal Rule the start of phase III is day 23.


Chart 3 CycleProGo (2013)

As computers became more common, people wanted to chart using that tool. CyclePro was released on CD-ROM. Charting could now be accomplished by using this electronic tool. Eventually CyclePro became an app on a smart phone and the name changed to CycleProGo (CPG). CPG was not just a tracking app; it actually computed and then applied the CCL rules for the determination of each phase and color coded the chart to make it easy to see the phases. Now the “art” of interpreting the chart needed to be quantified in the app. Many hours were spent developing the logic for CPG so that it would work and not give you incorrect phase interpretations. Forgotten or missed data can prevent an automated interpretation even though you can easily see a temperature and mucus trend, so it is necessary to use the automated interpretation as a tool to help with interpretation, but not rely on it wholeheartedly. The app is actually more conservative in applying the rules than we people are. This same 1986 cycle charted in the CPG app starts phase III on cycle day 23.


Chart 4 PeakDay (2023)

This year CycleProGo became PeakDay. The chart in PeakDay remains the same; the only change is the way observations and temperatures are input into the app. The chart displays the temperatures in boxes again, going back to the earlier chart. The convenience of using an app allows you to take the chart with you when you are away from home on travel and makes it easy to record observations throughout the day. You no longer need to remember at the end of the day what mucus you observed at 6 am!

PeakDay has the ability to show a big picture view of the fertility cycle to identify trends by viewing multiple charts at once and comparing data. These trends can help establish goals for better charting and improved health. There is also a wide range of data that can be entered alongside fertility information that can help explain outliers or show possible connections to abnormal chart data.


Yes, there can be outages using the app, your phone may lose battery, or other technical problems. You also probably lost or forgot your paper chart at times as well. However, difficult cycles are difficult no matter if viewed on the app or on paper. Sometimes, when the chart is difficult to interpret, you can copy it from the app to a paper chart just to see if you can find the trends better. The wife could chart on paper and the husband input your observations in the app just to “test” it out. For many users, it didn’t take too long to leave the paper chart behind and just use the app! It’s also easy to share the login with your spouse so you each can view your chart at any time. The information is more easily accessible which means couples can communicate and use the information more frequently towards the end goal of strengthening their relationship.

The adage “The more things change, the more they stay the same” is true for NFP use as well. No matter how you chart, or where you chart, you have the same goal in mind and need to prayerfully discern God’s calling for this cycle. As you can see on these different charts, the interpretations did not change. It is more about the way in which the experience of charting has changed.