jpg ratio ???

Print size will be dependent on image resolution. Image resolution was determined the instant you took the picture. Aspect ratio will have nothing to do with it. The aspect ratio comes into play when you decide what size print you want. As example, lets say you are using a Nikon D7000. This camera has a standard 3:2 aspect ratio. Recording the highest resolution possible you will get a file that is 4928x3264 <------ this IS your resolution. Period. And it is in the 3:2 aspect ratio. This means that the full area of the image captured is going to be a 6x4, or 12x8, or 24x16, etc, print. To print an 10x8 means changing the aspect ratio. In other words, you will crop the image to a 5:4 aspect ratio. When you do this, you lose resolution but only because you are cropping away an area that isn't going to show up because of the new aspect ratio. In other words, you haven't lost any quality, just quantity of pixels. As to how large of a print you can get all depends on the original resolution of the image and who is doing the printing. In most cases, print labs will let you know if you do not have enough resolution for the size of print you are attempting. But again, this resolution was set when you took the image and there is very little you can do about it in post-processing.