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.
For mid-grade, coated metal roofing, one might expect to pay up to $4.00 per square foot, with copper tipping the scales at over $6.50 per square foot. Of course, prices fluctuate according to the market price of the various metals used, as well as their availability for metal roofing manufacturing.