You may know much of the information below but I would like to share it with the masses as some are not aware of some of the technical reasoning behind the answer.
As I am an engineer and have a degree in mathematics, I believe I can be overly helpful. As I mentioned, this same sensor size issue is one that effects me greatly as a Nikon D2X guy wanting the same shallow Depth of Field as a full frame piece of film. One interesting point to those that don't know is to note that a 35mm piece of film does not measure 35mm in either direction. It really measures 24 x 36mm in film as it is double frame (height) of the old 18 x 24 movie film.
I think it is also important to note that magnification is done through the lens and the cropping factor (something invented by communists like Nikon / Sony to keep costs down and customer bases up) simply means the same size image comes through the same lens but some of that image spills past the edges of the sensor and into "nowhere" land off the sensor. An advantage of smaller sensors, aside from cost, is the edges of the lens (full frame sensors will see this) will vignette / darken as they can not disburse the light as efficiently as the center glass can. Simply understanding the concept of why fiber optic lines require a sheathing layer helps explain this refraction issue.
Besides sensor cost, please note that smaller sensors require smaller lens, also keeping lens cost and weight down. The issue of economics drives is what drives digital cameras anyway. Let's face it, if we really cared about Depth of Field or image quality, we would be shooting medium format Hassleblads!
In cameras like my D2X, it makes sense that the image quality is high, not because of any cropping factor, but simply that the receptors on the CMOS sensor are very small and close together. Nikon offers the highest image definition of any digital camera on the market simply because the sensors provide a finer image. Nikon leaves Canon in the dust when measuring resolving power simply because of this reason. The D2X has the highest resolving power of any digital camera. One note to remember is the Glamor business doesn't want resolving power as we don't want to see flaws in skin anyway. Black scarf filter anyone? NASA on the other hand uses D2X's to shoot the bottom of the shuttle as they do want resolving power. Something about things hanging off the bottom of their vehicle and 17,000 mph. The problem with the smaller sensors is when an image is "stretched" to be the same image size as a full frame camera it looks as if the resolving detail is not the same quality as the full frame camera. This effect was demonstrated in a previous post where two images (one D2X and one Mark II DS) where shown next to one another. The flaw in that remonstration is the Nikon camera would have to be further away or the image cropped to give the same starting point image.
To answer your question about sensor size cropping factor, the issue is slightly more complex that just that of sensor size as, for example, the Nikon has a sensor height of apx. 24mm and a Mark II DS has a sensor size of apx. 36mm. Simply dividing 36 / 24 gives you 1.5, or an apparent 1.5 crop factor. Just like horsepower of a car, you can measure power at the tire or the engine. You get different numbers depending on the point of measure. With cameras, you can measure the image at the sensor or on the final digital file. The only issue to keep in mind is that the image size has little to do with sensor size and more to do with pixel size and pixel count. Just as an example, there is an interesting article explaining this resolving power at:
To underscore the issue, please note that neither Nikon nor Canon define their image size by sensor size but rather by pixel count. To calculate a true comparison, you would need to know the pixel count and the pitch size of each photosite on the sensor.
All that being said, if the pitch size is somewhat similar in your question, simply 24 / 5.32 for an answer of around 4 1/2 or 5. I would dare to add that a sensor so small would undoubtedly have as fine a pitch count as the full frame camera as I suspect price / cost was a driving force to manufacture such a small sensor in the first place.
I still want a Canon D5 because the pixel count and photosite pitch size allow me to fit the image I want onto the sensor at a closer range than my Nikon therefore, blurring the background (similar to 1 1/3 greater stops) at a wide open F Stop.
Too much information?