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RoomCalc guides

Paint and drywall questions answered with the same arithmetic the calculators use.

Painting new drywall: primer and coats

One coat of drywall primer, then two coats of paint. Primer goes on at about the same rate as paint, roughly 350 sq ft per gallon, so a 12 × 12 ft bedroom with 8 ft ceilings (477 sq ft of walls and ceiling) needs about 1 gallon + 2 quarts of primer and 3 gallons of paint for two coats.

How much paint for one wall

A 12 × 8 ft wall is 96 sq ft, so one coat takes about 2 quarts and two coats about 1 gallon. Multiply the wall's width by its height, times the number of coats, and divide by 350, the square feet a gallon covers.

How much paint for a ceiling

A ceiling's area is the room's length times its width. A 12 × 12 ft ceiling is 144 sq ft, so one coat takes about 2 quarts and two coats about 1 gallon, at 350 sq ft per gallon. A textured or popcorn ceiling can take 30 to 50 percent more.

How much drywall for a garage

A two-car garage of 24 × 24 ft with 9 ft walls has about 1,307 sq ft to cover once the overhead and entry doors are taken off: 30 sheets of 4 × 12 ft or 45 of 4 × 8 ft with 10% waste. Code requires at least 1/2 in board on the wall shared with the house, and 5/8 in Type X on the ceiling if there is a room above.

Frequently asked questions

How many coats of paint does new drywall need?
One coat of drywall primer, then two coats of paint. Primer goes on at about the same rate as paint, roughly 350 sq ft per gallon, so a 12 × 12 ft bedroom with 8 ft ceilings (477 sq ft of walls and ceiling) needs about 1 gallon + 2 quarts of primer and 3 gallons of paint for two coats.
How much paint do I need for a 12x8 wall?
A 12 × 8 ft wall is 96 sq ft, so one coat takes about 2 quarts and two coats about 1 gallon. Multiply the wall's width by its height, times the number of coats, and divide by 350, the square feet a gallon covers.
How much paint do I need for a ceiling?
A ceiling's area is the room's length times its width. A 12 × 12 ft ceiling is 144 sq ft, so one coat takes about 2 quarts and two coats about 1 gallon, at 350 sq ft per gallon. A textured or popcorn ceiling can take 30 to 50 percent more.
How many sheets of drywall do I need for a 2 car garage?
A two-car garage of 24 × 24 ft with 9 ft walls has about 1,307 sq ft to cover once the overhead and entry doors are taken off: 30 sheets of 4 × 12 ft or 45 of 4 × 8 ft with 10% waste. Code requires at least 1/2 in board on the wall shared with the house, and 5/8 in Type X on the ceiling if there is a room above.

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