If you are asking about how the megapixels are calculated then what you need to know is that they are rounded off. Most cameras which are 24mp are in fact slightly over 24 and the exact amount over 24 varies slightly. The same with 20mp cameras.
Some cameras have different aspect ratios and how many mega-pixels you get depends on how close to this ratio your selected image format is. For example if your camera's sensor has a 4:3 aspect ratio but you select a 16:9 ratio to match your TV then your resulting image will have around 20% fewer pixels. This is because you are essentially cutting out part of the image in the camera in the same way you would do this in photoshop.
1920 x 1080 would be 2.07 Megapixils and the number is calculated by multiplying the number of horizontal pixels by the number of vertical pixels, Hope this helps!
And also, 'megapixels' is not an absolute indicator of image quality.
I have a 15 year old Olympus 3.3 megapixel that will outshine newer cameras at 8 megapixels.
What camera/phone/thingy is this we're talking about?
If you are asking about how the megapixels are calculated then what you need to know is that they are rounded off. Most cameras which are 24mp are in fact slightly over 24 and the exact amount over 24 varies slightly. The same with 20mp cameras.
Some cameras have different aspect ratios and how many mega-pixels you get depends on how close to this ratio your selected image format is. For example if your camera's sensor has a 4:3 aspect ratio but you select a 16:9 ratio to match your TV then your resulting image will have around 20% fewer pixels. This is because you are essentially cutting out part of the image in the camera in the same way you would do this in photoshop.