Exterior Paint Calculator
Gallons and Cost for Any Exterior
Calculate exterior paint gallons for house siding, fascia, soffits, and trim. Enter wall height, perimeter, and surface type — body and trim gallons appear instantly using MPI Repaint Manual coverage benchmarks.
Ready to estimate your exterior? Enter wall height and perimeter below — separate body and trim gallon totals calculate instantly with MPI-standard surface rates.
Wall height: ground to eaves. Perimeter: total exterior linear feet around the house foundation.
Vinyl, fiber cement, or primed hardboard siding — MPI benchmark
Trim calculated at 375 sq ft/gal (smooth boards). Trim area = Perimeter × 0.5 ft eave depth.
Standard — full repaint, new surface, or colour change
Exterior economy: $30–$50 · Mid-range: $50–$80 · Premium: $85–$120+
Enter wall height and perimeter
to see exterior gallons needed
Related Construction Calculators
More tools for accurate project estimation
The exterior paint formula
Exterior paint estimation uses perimeter-based geometry rather than individual wall measurements. Multiplying the full building perimeter by the wall height gives the gross wall area — a faster and sufficiently accurate method for standard rectangular homes. Gable ends, dormers, and non-rectangular footprints require individual face calculations that are then summed.
Exterior Paint Formula
Body Area = Perimeter × Wall Height | Trim Area = Perimeter × 0.5
Body Gallons = ⌈(Body Area × Coats) ÷ Coverage Rate⌉
For a 1,500 sq ft single-story house (perimeter ~140 ft, 9 ft wall height) with smooth vinyl siding: body area = 140 × 9 = 1,260 sq ft. At 375 sq ft/gal for 2 coats: 1,260 ÷ 375 × 2 = 6.72 gallons → order 7 gallons of body paint. Trim: 140 × 0.5 = 70 sq ft ÷ 375 × 2 = 0.37 gallons → order 1 gallon of trim paint. Total: 8 gallons across two products.
The 0.5 ft trim multiplier is a standard estimation approximation for the combined fascia board and soffit panel of a typical residential eave — roughly 3–4 inches of fascia plus 4–6 inches of soffit. For unusually wide soffits (12 inches or more), measure the actual soffit width and use that value instead. Our guide to calculating exterior paint covers complex rooflines and two-story elevation measurement in full.
Coverage rates by surface type
Exterior surface porosity is the dominant variable in coverage rate. Smooth factory-finished siding absorbs almost nothing; rough masonry acts as a sponge. The difference between smooth siding (375 sq ft/gal) and CMU block (125 sq ft/gal) means the same gallon of paint covers three times the area on smooth surfaces versus masonry — a 3× difference in material cost and total project outlay for the same square footage.
| Surface Type | Coverage Rate | Typical Product | Notes |
|---|---|---|---|
| Smooth vinyl / fiber cement siding | 350–400 sq ft/gal | 100% Acrylic Latex | Factory-finished surface; minimal absorption |
| Painted wood clapboard | 300–350 sq ft/gal | Acrylic Latex or Alkyd | Grain and condition affect absorption |
| Bare / weathered wood siding | 250–300 sq ft/gal | Penetrating Acrylic or Alkyd | UV-degraded fibres absorb heavily; prime first |
| Rough stucco / EIFS | 150–200 sq ft/gal | Elastomeric or Masonry Acrylic | Deep texture profile multiplies surface area |
| Concrete masonry unit (CMU) | 100–150 sq ft/gal | Block Filler + Masonry Paint | Block filler first coat mandatory on bare CMU |
| Brick (painted) | 150–200 sq ft/gal | Masonry Acrylic | High porosity; alkali-resistant primer required on new brick |
| Fascia / soffit boards | 350–400 sq ft/gal | Exterior Trim Paint (urethane alkyd) | Smooth primed surface; use trim-specific product |
For rough stucco and masonry surfaces, this calculator's 175 sq ft/gal and 125 sq ft/gal defaults reflect the heavily textured end of those ranges. If your stucco is smooth or lightly sand-finished rather than heavy aggregate, you may achieve 200–225 sq ft/gal in practice. Use the paint coverage calculator to enter a custom spread rate if your surface falls between the standard categories.
Fascia, soffit, and trim
Exterior trim — fascia boards, soffit panels, window casings, and corner boards — requires a distinct product from body siding paint. Exterior trim paint is formulated with urethane or advanced cross-linking acrylics to produce a harder, tack-free surface that resists dirt accumulation, gutter abrasion, and moisture pooling at horizontal surfaces. This product engineering commands a 15–20% price premium per gallon over standard exterior body paint.
The standard coverage rate for exterior trim paint on smooth fascia and soffit boards is 350–400 sq ft/gal — matching the rate for smooth siding. The area is small relative to the body but disproportionately visible: fascia boards at eave height are at eye level from the street and any missed spots, runs, or colour variation are immediately apparent. This calculator applies a 375 sq ft/gal rate for trim, which is the practical midpoint benchmark.
| House Size | Eave Perimeter (est.) | Trim Area | Gallons (2 coats) |
|---|---|---|---|
| Small (1,000 sq ft, 1-story) | ~110 lin ft | ~55 sq ft | 1 gal |
| Standard (1,500 sq ft, 1-story) | ~140 lin ft | ~70 sq ft | 1 gal |
| Large (2,000 sq ft, 1-story) | ~170 lin ft | ~85 sq ft | 1–2 gal |
| Two-story (2,500 sq ft) | ~160 lin ft | ~80 sq ft eaves + gable trim | 2–3 gal |
For a standard 1,500 sq ft single-story house with 100–150 linear feet of eaves, the combined fascia and soffit typically requires 2–3 gallons of trim paint for a 2-coat application. The trim gallon figure from this calculator uses the formula: Perimeter × 0.5 ft ÷ 375 sq ft/gal × coats. Use the primer calculator to add a primer gallon estimate for any bare wood trim that is being repainted after stripping.
When to add a primer coat for exteriors
Exterior primer is not optional on any surface condition beyond a sound, intact, recently painted substrate in DSD-0 condition. The MPI Repaint Manual defines four conditions that mandate primer regardless of topcoat quality.
| Surface Condition | Primer Required? | Primer Type | Rationale |
|---|---|---|---|
| Sound existing paint (DSD-0) | Optional | Bonding primer if sheen change | Direct topcoat acceptable on intact coating |
| Bare or weathered wood | Required | Exterior Alkyd or High-Adhesion Acrylic | Binds UV-degraded cellulose fibres |
| Bare new masonry / CMU | Required | Alkali-Resistant Masonry Primer | pH 11+ concrete burns acrylic topcoat (saponification) |
| Glossy existing surface | Required | High-Adhesion Bonding Primer | Acrylic cannot bond to slick enamel without mechanical bite |
| Previously painted (DSD-2/3) | Required | Stain-Blocking or Bonding Primer | Deteriorated surface needs fresh adhesion foundation |
Adding a primer coat to an exterior project increases the total gallon requirement by the primer volume — typically calculated at the same coverage rate as the topcoat for the same substrate. Use the paint cost calculator to model the cost impact of adding a primer system alongside body and trim topcoats, or the primer calculator for a standalone primer estimate by surface area and substrate.
Frequently asked questions
Does paint brand affect coverage rate significantly?
Yes — premium exterior paints achieve 400 sq ft/gal on smooth primed surfaces versus 350 sq ft/gal for economy grades, due to higher volume solids content. However, surface type is a far larger variable than brand. A premium paint on rough stucco still drops to 150–200 sq ft/gal because substrate porosity dominates. Brand matters most when comparing the same substrate across quality tiers, where the volume solids difference compounds across many gallons.
How long does exterior paint last before repainting?
Quality acrylic latex exterior paint lasts 7–10 years on smooth siding under average UV exposure. Wood clapboard may need attention at 5–7 years as substrate movement stresses the film. Stucco systems last 5–7 years before chalking becomes significant. Masonry with elastomeric coatings can reach 10–15 years. Southern and high-altitude climates with intense UV exposure reduce these intervals by 20–30%.
What happens to paint applied below 50°F?
Latex paint applied below 50°F (10°C) fails to form a continuous film. Acrylic polymers require a minimum coalescence temperature — below this threshold the paint dries without proper cross-linking, producing a chalky, brittle film that will peel within one to two freeze-thaw cycles. PCA guidelines require that both air and surface temperatures remain above 50°F during application and for at least 4 hours after application is complete.
Is two coats always better than one thick coat?
Two standard coats always outperform one thick coat. A thick single coat traps solvent vapour, causing bubbling and solvent pop as the surface skins over before the interior film dries. Paint manufacturers base durability warranties on achieving 1.5–2.0 mils dry film thickness per coat. Applying twice the wet film in one coat does not produce twice the dry film — the excess material sags, skins, and cures poorly throughout the film depth.
How do I account for dormers and gable ends?
For gable ends, calculate the triangle area: (base × height) ÷ 2, and add each gable to your total wall area. For dormers, calculate each dormer face as a rectangle (width × height) and add them. On a complex roofline, sketch each elevation as rectangles and triangles, calculate each face individually, and sum the totals before entering as your area figure rather than using the perimeter formula.
References
Master Painters Institute. (2025). MPI Maintenance Repainting Manual (RSM). MPI Publications.
Painting Contractors Association. (2023). PCA Standard P1 — Touch Up Painting and Damage Repair, and Definition of a Properly Painted Surface. PCA Industry Standards.
Angi. (2025). 2025 State of Home Spending Pulse Report. Angi Research.
Bureau of Labor Statistics. (2025). Occupational Employment Statistics — SOC 47-2141: Painters, Construction and Maintenance. U.S. Department of Labor.