Exterior paint calculator

Calculator to estimate how many gallons of exterior paint to buy for the project

Input parameters
Wall dimensions
Wall 1
Wall 2
Wall 3
Wall 4
Wall 5
Wall 6
Wall height H1
Wall length L2
Substructions S3
Paint properties
Coverage (ft2/gallon)4
# of coats5
Waste factor6


Computed parameters
Total paintable area7
Gallons of paint to buy8

Exterior paint calculator estimates total paintable area and quantity of exterior paint in gallons to buy for up to four rectangular and two triangular walls at a time.

Calculated numbers are accurate for painting simple houses with gable roof. For complex exterior painting projects, including painting custom designed exterior elements on house walls, all parameters should be adjusted based on work complexity. All computed numbers in the calculator are rounded to the nearest bigger number.

Input parameters:

1 H – Height of house wall in feet. Inches values should be entered as real number means 3 inches = 0.25 feet; 6” = 0.5’; 9” = 0.75’ and so on. Fractions must be converted to decimals.

2 L – Length of house wall in feet. Input real numbers only. Use decimals, but not fractions values.

3 S – Subtractions on the wall in square feet. In subtractions should be included all areas on walls which shouldn’t be painted, including windows and doors.

4 Every manufacturer provides an average coverage for particular paint in square feet per gallon. But actual paint consumption not solely depends on type and quality of paint. Method of paint application, type of paint roller, pile depth of roller cover, type of paint sprayer, size of a spray gun tip, condition of surface and who will complete the project will affect actual usage of exterior paint.

5 Number of paint coats depends on surface condition at a first place. Typically, well prepared exterior walls, with no color changes, will be professionally sprayed with airless sprayer one time. In some cases, second coat of paint application mighty be necessary for the best results.

6 Adding 10% for waste is typical for performing basic exterior painting projects. Under ideal conditions experienced painter could decrease paint waste to 5%. In some cases, especially during complex custom projects waste factor could be greatly increased.

Computed parameters:

7 Total paintable area is an actual walls area in square feet which should be painted.

8 Gallons of paint to buy is an actual quantity of exterior paint necessary to purchase for performing basic painting project. Computed number includes defined waste factor.