That depends on what the starting gravity was. The alcohol content is calculated using the diference between the starting & finishing gravities.
There's a calculator on the Grumpy's site that lets you plug in values & see how they affect various parameters.
The more sugars (malt, dextrose, sucrose) etc in the recipe (with respect to the size of the batch of course) the higher the OG. The higher the OG, the greater the potential for alcohol production. It's not as simple as just tipping more sugar in tho, because you then have to account for adding extra hops for bitterness.
Anyway, your question was about the relationship between gravity and alcohol, the calculator on Grumpys will do it for you.
Cheers,
PoMo.
EDIT: oops, forgot link.
EDIT2: just saw RobW's post. Beat me to it by 2 mins