If you order your images to be returned on a CD they are 8 inches at 300 dpi on the short dimension of the image. Depending on the aspect ratio (the shape) the most common picture sizes will be…
- 8×8 at 300 dpi
- 8×10 at 300 dpi
- 8×12 at 300 dpi
Images delivered online are more compressed than their CD counterpart though ultimately you will see no difference.