gallonsquare feet. Other websites say a gallon will cover 400-450 square feet of smooth surface. If you've got a rough textured surface or surfaces which need 2 coats of paint, a gallon will cover about 200 square feet. The above answer may be a general rule of thumb.
Highly rated roofing contractors tell us that asphalt is the most affordable roofing option, followed by wood, tile, metal, and slate. Materials for a metal roof can cost up to $350 to $1,500 per 100 square feet. Angie's List members recently reported paying an average of $12,236 for a metal roof installation.
Metal roof installation costs around $5 to $15.00 per square foot or more. This works out to a total metal roof price of roughly $7,500 to $22,500 for a 1,500 square foot roof. It's possible in many cases to install a metal roof over old asphalt shingles.