What is a T/C Ratio?

November 1, 2019     By Teri Karl

You have the Premom app, and you’re ready to get started tracking your ovulation . . .  but what on Earth is a T/C ratio?

Simple answer? The typical ovulation tests have 2 lines: the test line (T), and the control line (C). The T/C ratio simply compares the color intensity of the T line to the color intensity of the C line.

When looking for your LH peak, you are aiming for a ratio of 1.0, when the test line is as dark as the control line.  A test line lighter than the control line will be less than 1.0.  A test line darker than the control line will be darker than 1.0.

However, besides giving a positive or negative result, ovulation tests can also help you track your LH surge, showing an increase or decrease in LH levels as you continue to test.  Though they will not give you an exact LH level (only Premom quantitative tests can do this), they can help you get a general idea of the ups and downs of your personal ovulation cycle, even helping you recognize the approach of your surge as your levels near .5 and above.

It’s important to know that the exact ratio value is not important.  Always look for the last, darkest test line. Aim for the standard peak ratio of 1.0, but know that some women do peak lower (between .8 and 1.0), and others may peak higher than 2.0! 

Since ratios can vary from woman to woman and even cycle to cycle, the key is to keep testing, even after what appears to be “positive” or “peak” to make sure you’ve found your true peak and that your surge is over.  In other words, keep testing until you see your LH levels heading back down and staying down.  The app is also looking for this and will not designate “peak” until the uploaded test after your peak.  To learn more about how the Premom app adjusts to different women with different LH levels, read more here.

More questions?  In your Premom app tap “FAQ” in settings for other common questions or tap “Support” and get a personalized answer to your specific questions.

ovulation, peak, ratio, t/c ratio, test line