APS-C or Advanced Photo System type-C is one of the most popular type of an image sensor widely used in consumer level photo cameras.
APS-C sensor size
It is more or less equal in size to the size of negatives which are used in an analog photography. The dimensions of these negatives are 25.1 × 16.7 mm (while 35 mm standard film measures 36×24 mm) and their aspect ratio is 3:2. APS-C sensor size from manufacturer to manufacturer varies between 20.7×13.8 mm to 28.7×19.1 mm.