Ceiling paint estimator Multiply the length of the ceiling times its width to find its area. 2. Divide that number by 350 (the estimated square feet covered per gallon) to figure out how many gallons of paint you need. For this example, you want to buy 1 gallon of ceiling paint for a single coat.Click to see full answer. Similarly, how much paint do I need for a 12×12 ceiling?You’d need about 1.5 gallons of paint to cover a 12’x12′ room with 8-foot-high walls.One may also ask, how many square feet will 5 gallons paint cover? Check the paint container to determine the estimated coverage. Generally, a quart of paint covers about 100 square feet, and a gallon of paint covers 400 square feet. Similarly, you may ask, how much paint do I need calculator? One gallon can of paint will cover up to 400 square feet, which is enough to cover a small room, like a bathroom. Two gallon cans of paint cover up to 800 square feet, which is enough to cover an average size room. This is the most common amount needed, especially when considering second coat coverage.How much exterior paint do I need for a 1500 square foot house?So, an average 1200 to 1500-square-foot rambler home would require from 12-15 gallons of good-quality paint for about two coats. This number also includes the painting for the siding, overhangs, and soffits. Prepare for the accent trim. We need 2 to 3 gallons of paint for painting the gutters, fascia, and window trim.