Exterior Paint Calculator
How much exterior paint do you need? This free exterior paint calculator gives homeowners and pros instant gallon estimates for siding, trim, and doors — separately — based on home dimensions and surface texture (vinyl, wood, stucco, or brick).
Exterior paint mistakes cost more than interior ones. Stucco swallows nearly twice the paint of smooth siding (150–200 sq ft/gal vs. 350+), and skipping primer on bare wood means 3 coats instead of 2. A single missed gallon on a 2-story house can mean climbing the ladder twice.
Calculates primer + 2 coats separately per PDCA standards, and runs in under a minute — no signup.
Exterior Paint Calculator
Calculate exactly how much paint and primer you need.
Project Details
Non-porous, smooth surface. Best coverage rates.
Always required for bare wood, masonry, and metal. Can be skipped on previously painted surfaces in good condition with same/darker colors.
Exterior paint coverage varies by surface: 350-400 sq ft/gal for smooth siding, 250-300 sq ft/gal for textured surfaces, and 200-300 sq ft/gal for rough stucco or brick. Primers cover 200-300 sq ft/gal regardless of surface type.
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View Product (paid link)🎨 Coverage by Surface Type
| Surface Type | Paint (sq ft/gal) | Primer (sq ft/gal) | Notes |
|---|---|---|---|
| Smooth Vinyl Siding | 350-400 | 200-300 | Best coverage, minimal absorption |
| Fiber Cement Siding (Smooth) | 350-400 | 200-300 | Similar to vinyl when sealed |
| Wood Siding (New) | 300-350 | 200-300 | Smooth wood, pre-sealed |
| Wood Siding (Weathered) | 250-300 | 200-300 | Higher absorption, needs more coats |
| Textured Surfaces | 250-300 | 200-300 | Rough sawn wood, textured fiber cement |
| Rough Stucco | 200-300 | 200-300 | Heavy texture increases paint usage |
| Brick (Unsealed) | 200-300 | 200-300 | Very porous, requires multiple coats |
Key Takeaway
Primers universally cover 200-300 sq ft per gallon regardless of surface type. This reduced coverage ensures proper sealing and adhesion. Paint coverage varies by surface texture and porosity.
🔧 Application Method & Waste Factors
Brush & Roller
Airless Sprayer
Conventional Air Spray
HVLP Sprayer
🧮 Example Calculation
Two-Story House with Wood Siding
Step 1: Calculate wall area
Perimeter: 150 feet
Average height: 20 feet (two stories)
Total: 150 × 20 = 3,000 sq ft
Step 2: Deduct openings
Doors & windows: ~400 sq ft
Paintable area: 3,000 - 400 = 2,600 sq ft
Step 3: Calculate primer needed
Coverage: 250 sq ft/gal (mid-range for primer)
Primer: 2,600 ÷ 250 = 10.4 gallons
With 10% waste: 10.4 × 1.10 = 11.5 → 12 gallons
Step 4: Calculate paint needed (2 coats)
Coverage: 275 sq ft/gal (weathered wood)
Per coat: 2,600 ÷ 275 = 9.5 gallons
Two coats: 9.5 × 2 = 19 gallons
With 10% waste: 19 × 1.10 = 20.9 → 21 gallons
Total Materials:
• Primer: 12 gallons
• Paint: 21 gallons (2 coats)
📚 Industry Standards
PCA Standards (formerly PDCA)
The Painting Contractors Association provides guidelines for exterior paint coverage rates, surface preparation requirements, and quality standards. Standard coverage: 350-400 sq ft/gal for smooth surfaces.
ASTM D3274 - Evaluating Degree of Surface Disfigurement
Standard guide for assessing chalking of exterior paint films. Determines when repainting is necessary based on surface degradation.
ASTM D6577 - Measuring Wet Film Thickness
Standard for determining proper paint application thickness. Ensures adequate coverage and durability for exterior surfaces.
Surface Preparation Standards
SSPC (Society for Protective Coatings) standards specify proper cleaning, scraping, sanding, and priming procedures for various exterior surfaces. Proper prep is critical for paint adhesion and longevity.
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Frequently Asked Questions
How much does exterior paint cover per gallon?
Smooth siding covers 350-400 square feet per gallon. Textured surfaces cover 250-300 square feet per gallon. Rough stucco or porous brick covers 200-300 square feet per gallon. Coverage depends on surface texture, porosity, and application method.
How much does primer cover per gallon?
Primers universally cover less than topcoats, standardizing at 200-300 square feet per gallon across all manufacturers regardless of surface type. This reduced coverage accounts for better penetration and surface sealing.
How many coats of exterior paint do I need?
Most exterior projects require 2 coats. Previously painted surfaces in good condition may need only 1 coat if using high-quality paint and similar colors. Bare wood, new siding, or dramatic color changes require 1 primer coat plus 2 finish coats.
Should I paint trim and siding separately?
Yes, calculate trim separately. Trim, fascia, and soffits use different paint types (often semi-gloss vs satin for siding). Trim typically requires 1-2 quarts per 500 square feet of siding. Doors and shutters are calculated individually as accent areas.