I need this information because I would like to use the Computer Modern fonts in a Windows application that I am developing. The GUI library that I am using (wxWidgets) requires that all lengths be specified in pixels.
According to the documentation of TFtoPL (see Section 10, p. 205), 7227 TeX points correspond to 100 inches (254 cm). To convert inches into pixels, one must know the resolution (in ppi = pixels per inch) of the rendering device (e.g., a monitor or a printer).
The final formula is:
[Size in pixels] = [Size in TeX points] * [Device resolution in ppi] / 72.27
"TeX points" are an absolute length measure, "pixels" depend on the display resolution. The same document can be displayed on varying screens, and even at different magnifications. Or be printed on a inkjet printer, a high-end laser printer, or a professional typesetter. Wildly different pixel sizes.