canon super 50 zoom

28.07 square millimetres. why do you ask?

The size of the 1/2.3-inch sensor is 6.17 mm x 4.55 mm = 28.07 square millimetres.
The Canon USA website gives the total pixels as "approx 12.8 Megapixels" and the effective pixels as "approx 12.1 Megapixels" and the final picture contains 4,000 x 3,000 pixels = 12.0 Megapixels.
If you assume that the 6.17 mm x 4.55 mm (not exactly a 4:3 ratio) corresponds to 12.8 MP, then the 12.0 MP in the final 4,000 x 3,000 image would correspond to
5.92 mm x 4.44 mm = 26.3 square millimetres.
I use dimensions that are calculated in a similar manner for my SX30 in order to determine magnification.  This is probably not very accurate for wide-angle, where the image is quite distorted, as can be seen in RAW photos from the SX50.

If we compare the actual FL and the eguivalent FL (4.3-215mm vs. 24-1200mm) we'll get a 5.58x cropfactor, and if we divide the diagonal of a 24x36mm sensor (43.27mm) by 5.58 we'll get 7.754mm, meaning that the SX50 sensor should be app. 6.20x4.65mm.

EXACTLY as other super zooms, like FZ200, P510, SP-820UZ, SX40 and many others: 1/2.3".

Thank you Steen,
    I have been measuring magnifications for close-up lenses (at infinite camera focus) and finding that they were 3% to 5% smaller than measured values.  Using your numbers for the sensor size, the measured values are now only 0% to 2% smaller, which is much better agreement.