er... it depends on the resolution to be honest. 72dpi images will print out either very small or large and pixellated, higher resolution images will end up ok. If you have photoshop, open up your image and go into edit/image size on the top menu. the setting for a high resolution a4 image will be something like this:
Width: 20cm
Height: 28cm
Resolution: 300dpi
Often though, digital cameras take pictures at 72 dpi, but at super large printsize, so when you check the image size, it looks something ike this:
Width: 80cm
Height: 106cm
Resolution: 72dpi
This is fine as well, cos when you decrease the print size, the resolution increases.
Or - you could always just bring your camera in to a shop, get them to do a test print for you there and then, and judge by the results. You should also set your camera to its highest image setting if you plan on printing large images from it in the future.