How to find IC50/EC50 values using KaleidaGraph?

In order to calculate IC50 values, you need to plot the data and apply a General (user-defined) curve fit.

  1. Create your plot.
  2. Choose Curve Fit > General > Sigmoidal. This equation is the same as the Dose Response Logistic equation found in the IC50 folder (see below).
  3. Click the check box for each variable you want to fit.
  4. Click OK to apply the fit.
  5. KaleidaGraph will attempt to fit the data and should display a table containing the results, where m1 is the Ymin value, m2 is the Ymax value, m3 is the X value at mid-point of Y (IC50), and m4 is the slope of the curve at the midpoint.
  6. If you get a Singular Matrix Coefficient error message, it may be necessary to adjust the initial guesses for the unknown parameters.

KaleidaGraph also includes other curve fit equations that can be used to determine IC50 values. The IC50 curve fit equations are stored in the IC50 folder (within the Curve Fits folder in the Examples folder). These are individual text files that can be used within the General curve fit.

The equations are listed in the Help file. The easiest way to find it is to look up IC50 in the Index. You can also enter your own equation if the one you want to use is not provided.

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