This planning estimate works from a rectangular building footprint and includes an optional gable allowance.
01 / Formula
How this is calculated
Paint = ((perimeter × wall height × stories + gable area − openings) × coats) ÷ coverage02 / Assumptions
What the estimate assumes
- ✓The footprint is rectangular and story heights are equal.
- ✓Gable allowance is an editable percentage of wall area.
- ✓Complex bump-outs, dormers, trim, masonry, and detached structures should be measured separately.
03 / Worked example
See the math in context
A 40 × 28 ft one-story home with 9 ft walls has 1,224 sq ft of gross wall area before gables and openings.
04 / Guidance
Exterior surfaces vary
Rough masonry, stucco, shingles, and heavily textured siding may use more coating than smooth siding. Use the product’s stated coverage for your substrate and application method.
Questions
Frequently asked
Should I round up when buying paint?+
Yes. Paint is sold in fixed container sizes, and a small reserve helps with touch-ups, porous surfaces, and application loss. The calculator shows both the theoretical quantity and a practical purchase amount.
Does paint coverage include two coats?+
Coverage printed on a can is normally stated per coat. Two coats cover the same surface twice, so the calculator multiplies net area by the number of coats before dividing by the selected coverage rate.