Sorry, it only applies if the CCDs are of the SAME diameter. If you are familiar with 35mm cameras and lenses, it would be like comparing a 35mm lens with a Hasselblad 2 1/4" lens. The requirements are different for the different image sizes.
The Canon has a 3/4" sensor (more than 3x the Panasonic's)
The Panasonic has a 1/6" sensor so the mm's should be less.
There is no precise formula for converting from one to the other, as each manufacturer uses a different number of pixels as the actual capture size (even when the same size sensor is used): i.e. not all pixels are used, and some use more than others. It's just a general principle.
The sensor size does NOT tell you which is better in low light, contrary to popular opinion. They could be similar: you'd have to check them out side-by-side.