How to use this calculator
- Measure the wall perimeter and average height.
- Subtract doors, windows, and surfaces not being painted.
- Enter finish and primer coat counts.
- Use the product label’s stated coverage.
#2999 · Lifestyle & Home Tool
Exterior Painting Material Quantity Calculator
Estimate exterior finish paint and primer from building perimeter, average wall height, excluded openings, coat count, and stated coverage. The result separates finish and primer volumes and shows the paintable wall area, providing a transparent starting point before adjusting for texture, porosity, and application method.
Calculator
Wall dimensions and coverageFormula
Paintable area = perimeter × height − excluded area
Gallons = paintable area × coats ÷ coverage per gallon
Gallons = paintable area × coats ÷ coverage per gallon
What the result means
The calculated volume is a mathematical requirement before rounding to available container sizes. Finish paint and primer are shown separately.
Coverage varies with porosity, texture, application method, color change, and product. Use the actual label and keep primer and finish products separate.
Example calculation
A 160 ft perimeter at 10 ft high, less 240 sq ft of openings, leaves 1,360 sq ft. Two finish coats plus one primer coat at 350 sq ft per gallon require 11.66 gallons total: 7.77 finish and 3.89 primer.
Tips for better results
- Measure gables and unusually shaped sections separately.
- Use lower coverage for rough or porous surfaces.
- Do not subtract every small opening; cutting-in can offset the saved area.
- Round each product up to purchasable container sizes.
- Keep batch numbers consistent when appearance matters.
Frequently asked questions
Should I subtract every window from exterior wall area?
Subtract large excluded areas. Very small openings may not reduce paint use much because edge work and application loss remain.
How do multiple coats change the exterior painting quantity?
Each coat covers the paintable area again, so required volume increases directly with the coat count.
Should primer use the same coverage as finish paint?
This calculator uses one coverage input for planning. If the labels differ materially, calculate primer separately using its own coverage.
Why should calculated gallons be rounded up?
Paint is sold in fixed container sizes, and running short can create color or finish inconsistencies.
Does sprayer loss appear in the formula?
No separate sprayer-loss factor is included. Reflect expected application loss by using a conservative coverage rate.
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Coating quantity variables
| Variable | Unit and purpose |
|---|---|
| Paintable area | Square feet after exclusions |
| Coverage | Square feet per gallon per coat |
| Coats | Separate counts for finish and primer |