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How much paint to buy for painting certain room size?

How much paint to buy for painting a room?

Room size1
Number of doors2
Number of windows3
Paint amount4
For ceiling
For walls
10' x 10'
1
1
½
1
12' x 12'
2
1
½
1
14' x 14'
2
2
1
1½
16' x 16'
2
2
1
1½
20' x 20'
2
3
1½
2

1 Calculations made based on standard rectangular room dimensions with flat ceilings and 8 feet high walls.

2 Number of doors is a parameter which defines all doors in the room including entrance and closet doors. For calculating paint, 28” – 32” wide and 80” high door dimension were taken into account.

3 Number of windows defines all types of windows in the room. For calculations 36” x 54” window size was taken into account.

4 Amount of paint calculated as average number of gallons necessary to purchase for one coat of water-based paint application using 9 inches wide microfiber roller. Very high probability that on repaint projects one coat of paint application on walls will be insufficient and you always adjust amount on paint to purchase based on a number of coats necessary to apply. Some paints, including really dark red or blue colors should be applied even three times for proper covering the surface.

While shopping for an interior paint it is always better to buy more than less. Extra quarter of a gallon paint left after painting project completed can be used for touch-ups.

Accuracy

All numbers in the chart are estimated based on 400 ft2 coverage area by one gallon of paint. Estimated accuracy is high for smooth, and already primed or painted surfaces.

Actual paint usage might vary. Intentional application of thicker layer of paint for better coverage of rough surfaces will result in higher paint usage.

Estimating paint amount for painting closets

One gallon is sufficient amount of paint for one coat of paint application on walls and ceiling in three regular 2’ x 6’ closets with 28” wide double door.

Calculating amount of paint for painting kitchen and bathrooms

It is nearly impossible to foresee how much paint to buy for bathrooms and kitchen before getting an idea about actual surface area which has to be painted. Often close to 30% - 40% of walls area in 5’ x 7’ bathroom covered by tile and 35% – 50% of kitchen walls covered by cabinets and backsplash. Normally with one gallon of paint it is possible to paint walls in couple standard bathrooms accounting two coats of paint application. For standard up to 11 x 11 feet kitchen even half gallon of paint will be enough.

Spray vs brush and roller methods of paint application

Spraying ceiling and walls is a painting technique commonly used on a new construction projects while repainting 2 – 3 rooms in the house it is easier and less messy to use a paint brush and roller. Moreover, even on a new construction if walls are different colors many contractors spray ceilings only and roll colored paint on walls.

On average, airless paint sprayers have 0.31 – 0.47 gallons per minute flow rate and lack of skills can cause a huge amount of paint left on unintended surfaces such as masking paper or floor. In addition, quality sprayer has about 70% of paint transfer efficiency and repainting particular room(s) in the house with brush and roller is a way better option in comparison to using airless sprayer on such small home improvement project.