It is 640x480, but TVs crop the screen on the top and bottom by quite a bit. If you have a TV tuner, you'll see the difference - the network logos look like they're in the wrong place (not evenly spaced in the corner). Oh, and some TV can output at resolutions up to 800x600 (that's what I set my video card at when I output to the TV). I'm not sure if this helps you any, but I thought I'd share.
Squibby