Calculate Amount of Paint Needed

Step 1:
To calculate how much paint you'll need, begin by determining the square footage of area to be painted using the appropriate formula(s) based on the area(s) to be painted. Measure every aspect of the area to be painted and keep the following in mind:

• Many walls and other areas are not simply a straight, flat area and you will need to measure each separate area.Measure both sides and all edges of doors if you are painting both sides.Measure trim if it will be painted and keep in mind it probably isn't a flat surface.
  Surface area/paint coverage hints:
• Lap Siding - calculate wall width x height and multiply by 1.5
• Extremely weathered surfaces will absorb more paint and will therefore require more paint.
• Drywall and bare substrates will require two coats of paint - a primer (or first) coat and a finish (or second) coat. The surface will absorb more of the first coat than second coat and will therefore require more paint for the first coat.

Square: Side x Side = Total Area Example: 8' x 8' = 64 sq. ft.
Rectangle: Width x Length (Height) = Total Area Example: 8' x 4' = 32 sq. ft.
Triangle: 1/2 Base x Height = Total Area Example: 1/2 (30') x 10' = 150 sq. ft.
Circle: Diameter x Diameter x.7854 = Total Area Example: 25' x 25' x .7854 = 491 sq. ft.
Cylinder: (Circumference x Length) + Area of End(s) = Total Area Example: Circumference (3.14 x 20') x Length (40') + Area of 1st End (20' x 20' x .7854) + Area of 2nd End (20' x 20' x .7854) = 3140 sq. ft.
Sphere: Diameter x Diameter x 3.14 = Total Area Example: 20' x 20' x 3.14 = 1256 sq. ft.

Step 2:
Divide square footage by theoretical coverage per gallon as indicated on the paint label. The resulting number is the approximate number of gallons of paint you will need. (Theoretical coverage per gallon will be approximately 200 to 400 sq. ft. per gallon on most products; however, primer or first coats over weathered or bare substrates and drywall may be 150 - 200 sq. ft. per gallon.)

EXAMPLE:

Re-painting an entire room that measures 12' x 20' and has an 8' high ceiling. Paint selected has a theoretical coverage of 300 sq. ft. per gallon.

Wall 1	12'x 8'	96 sq. ft.
Wall 212' x 8'	96 sq. ft.
Wall 320' x 8'	160 sq. ft.
Wall 420' x 8'	160 sq. ft.
Ceiling12' x 20'	240 sq. ft.
Total	752 sq. ft.

752 total sq. ft. ÷ 300 sq. ft per gallon = 2.5 gallons. Purchase 3 gallons.

EXAMPLE:

Painting an entire room for the first time - walls and ceiling are drywall.

Room measures 12' x 20' and has 8' high ceiling.

Selected primer (first coat has a theoretical coverage of 175 sq. ft. per gallon.

Selected finish (second coat) has a theoretical coverage of 300 sq. ft. per gallon.

752 total sq. ft. ÷ 175 sq. ft per gallon of primer coat = 4.3 gallons of primer
752 total sq. ft. ÷ 300 sq. ft per gallon of finish coat = 2.5 gallons of finish

NOTES:

• Check the can of paint.  It will tell you the coverage (e.g. 300 square feet per gallon or 200 square feet per gallon, etc.