Exterior house paint should be measured elevation by elevation. Sum wall and gable surfaces, subtract substantial openings, separate substrates and colors, multiply each group by coat count, then divide by the chosen product's coverage.
Measure exterior elevations by substrate, subtract substantial openings, add gables and other painted planes, multiply each group by coat count, and divide by the selected coating's coverage.
Published: September 26, 2026
Last reviewed: September 26, 2026
Published by BuildYard. The guide reflects BuildYard's calculation methodology and editorial standards and does not replace project-specific professional advice.
Measure each wall rectangle and gable triangle independently.
Keep siding, masonry, stucco, trim, doors, soffits, and other coating systems separate.
Large windows and doors reduce field area, but their casing and trim may create separate paint quantities.
Do not subtract openings from one coating while forgetting their replacement trim area in another.
Multiply each net substrate area by its specified coat count.
Primer, spot-primer, and finish coats should remain separate order lines when products differ.
Divide coat area by the selected product's stated coverage and round to available container sizes.
Rough siding, masonry, spraying, wind, and back-rolling can change field consumption.
Check repaired areas, moisture condition, substrate preparation, and color changes before final ordering.
The area calculation does not determine coating suitability.
Estimate deck stain for boards, stairs, fascia, and rails using developed area, coat count, product coverage, and wood condition.
Read guide →Paint & FinishEstimate fence coating from run length, height, painted sides, developed board and rail area, coat count, and product coverage.
Read guide →Paint & FinishConvert baseboard, casing, fascia, and molding linear feet into developed paint area, then calculate coating quantity by coats and coverage.
Read guide →Illustrative field-paint example before gables, trim, other elevations, and substrate-specific adjustments.
| Step | Calculation | Result |
|---|---|---|
| Gross area | 2 × 40 × 10 | 800 sq ft |
| Openings | Subtract | 120 sq ft |
| Two coats | 680 × 2 | 1,360 sq ft |
| At 350 sq ft/gal | 1,360 ÷ 350 | 3.89 gal |
Current manufacturer data, supplier specifications, drawings, field measurements, applicable codes, permit requirements, and qualified professional guidance can take priority over a general-purpose planning estimate.