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.
1 Metal roofs cost anywhere from $3 per square foot to $20 per square foot or more (or $4,500 to $30,000 for a 1,500 square foot roof). 2  Aluminum roofing costs $6 to $12 per square foot ($9,000 to $18,000).  Steel roofing costs $3 to $10 per square foot ($4,500 to $15,000).