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 2 |
12' x 8' |
96 sq. ft. |
| Wall 3 |
20' x 8' |
160 sq. ft. |
| Wall 4 |
20' x 8' |
160 sq. ft. |
| Ceiling |
12' 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.
| Wall 1 |
12' x 8' |
96 sq. ft. |
| Wall 2 |
12' x 8' |
96 sq. ft. |
| Wall 3 |
20' x 8' |
160 sq. ft. |
| Wall 4 |
20' x 8' |
160 sq. ft. |
| Ceiling |
12' x 20' |
240 sq. ft. |
| Total |
|
752 sq. ft. |
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:
- When calculating how much paint you’ll need for your paint job, there are
many variables to consider. The information and examples provided here are meant to be a general reference only and are based on typical structures and typical coatings.
- Please refer to the paint label for detailed information regarding volume solids, suggested dry film thickness and theoretical coverage per gallon which will all affect quantity of paint needed, and ask your local paint store for assistance in determining the actual amount of paint you should purchase.
Columbia Paint & Coatings is providing this information merely as a public service to its customers and prospective customers. Columbia assumes no liability for the accuracy or completeness of this information.
