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
Not sure? Calculate your square footage →
Have gable ends? Get their area with the Gable Area Calculator →
Not sure how to measure paintable area with gables? See the take-off diagram
Non-porous, smooth surface. Best coverage rates.
Why does the surface change how much paint you need? See the coverage diagram
Always required for bare wood, masonry, and metal. Can be skipped on previously painted surfaces in good condition with same/darker colors.
Do you need primer, and how many coats? See the coating-film diagram
How to estimate exterior paint accurately
Most paint estimates miss for three reasons: the surface drinks more paint than expected, bare or weathered spots need primer, and the gable gets left out of the measurement. These engineering-style diagrams walk through each one — use the “see the diagram” links beside the inputs above to jump to the figure you need.
The coverage-by-surface chart is why the calculator asks what you are painting, not just the square footage. A gallon spreads nearly twice as far on smooth siding as on rough stucco, so surface texture and porosity — not the area math — are what throw off most paint estimates. Tell it the surface and the gallon count reflects how thirsty that surface really is.
The primer-and-coats detail explains why bare surfaces add a primer line and why the calculator defaults to two thin coats. Primer seals porous wood, blocks stains, and bonds to slick surfaces, and two thin coats hide better than one heavy one. Skip the primer on bare wood and the topcoat wicks in blotchy — more paint, worse result.
The paintable-area breakdown is why a gabled wall is measured in two pieces. The rectangle is width times wall height, and the gable adds a triangle on top, and only large openings are subtracted before area becomes gallons. Measure the rectangle alone and you under-buy the gable; the calculator adds both.
Calculation Formulas
Calculate perimeter of house, multiply by wall height, then subtract doors and windows.
Example:
40ft × 30ft house = 140ft perimeter × 10ft height = 1,400 sq ft - 200 sq ft openings = 1,200 sq ft
Rough or textured siding absorbs more paint than smooth surfaces. Multiply base area by texture factor.
Example:
1,200 sq ft × 1.3 (rough wood siding) = 1,560 sq ft adjusted area
Divide adjusted square footage by coverage rate per gallon. Smooth surfaces: 350-400 sq ft/gal, textured: 200-300 sq ft/gal.
Example:
1,560 sq ft ÷ 300 sq ft/gal (textured) = 5.2 gallons → round up to 6 gallons
Trim requires approximately 1 gallon per 50 linear feet for single coat coverage.
Example:
200 linear feet trim ÷ 50 = 4 gallons trim paint
Most exterior paint requires 2 coats. Add 1 coat if using primer. Dark-to-light color changes may need 3 coats.
Example:
6 gallons × 2 coats = 12 gallons total
Primer typically covers less than topcoat: 250-300 sq ft per gallon average.
Example:
1,200 sq ft ÷ 250 = 4.8 gallons → round up to 5 gallons primer
Standard Constants
| Constant | Value | Description |
|---|---|---|
| Smooth Siding Coverage | 350-400 sq ft/gal | Vinyl, smooth fiber cement, or painted surfaces |
| Textured Siding Coverage | 250-300 sq ft/gal | Wood lap siding, textured stucco, T1-11 |
| Rough/Porous Coverage | 150-250 sq ft/gal | Brick, rough stucco, rough-sawn wood, concrete block |
| Primer Coverage | 250-300 sq ft/gal | Sealing bare surfaces requires more material |
| Standard Door Size | 21 sq ft | 7 ft height × 3 ft width typical |
| Standard Window Size | 15 sq ft | 5 ft height × 3 ft width average |
| Recommended Coats | 2 | Two coats for durability and weather protection |
Note: All calculations include appropriate waste factors based on project complexity and material type. Results are estimates and should be verified by professionals before purchasing materials.
ASTM D3276 - Standard Guide for Painting Inspectors(ASTM D3276-15)
View StandardComprehensive guide for exterior paint inspection covering surface preparation, application methods, film thickness, and quality control for masonry, wood, and metal substrates.
Key Requirements:
- •Surface prep: Clean, dry, and stable before painting (moisture ≤15%)
- •Primer required: New wood, repairs, masonry, or substrate changes
- •Film thickness: 4-6 mils wet, 1.5-2.5 mils dry per coat minimum
- •Adhesion testing: Cross-hatch or pull-off test for quality assurance
- •Temperature: Apply when surface temp is 50-90°F, no rain within 24 hours
Vinyl Siding Institute (VSI) Paint Guidelines(VSI Standards)
View StandardGuidelines for painting vinyl siding to prevent heat warping. Requires specific Light Reflectance Value (LRV) ratings to avoid vinyl distortion from heat absorption.
Key Requirements:
- •LRV rating: Minimum 55 or higher (lighter colors only)
- •Dark colors prohibited: Can cause vinyl to warp from heat (up to 160°F surface temp)
- •Surface cleaning: TSP wash, rinse thoroughly, allow to dry
- •Paint type: 100% acrylic latex designed for vinyl and plastic
- •Warranty: Painting may void vinyl manufacturer warranty - verify first
PDCA - Painting & Decorating Contractors of America Standards(PDCA P1-P20)
View StandardProfessional painting standards for residential and commercial exteriors. Covers surface preparation levels, application methods, coating specifications, and quality benchmarks.
Key Requirements:
- •Surface prep levels: P1 (minimal) to P5 (maximum) based on condition
- •Two-coat minimum: Primer + finish or two finish coats
- •Drying time: 24 hours between coats at 70°F, longer in cold/humid weather
- •Application method: Brush, roll, or spray based on substrate and texture
- •Spot priming: All repairs, stains, and substrate changes before topcoat
National Roofing Contractors Association (NRCA) - Fascia/Soffit(NRCA Guidelines)
View StandardStandards for painting fascia, soffits, and trim boards that interface with roofing systems. Emphasizes moisture barriers and proper priming to prevent wood rot.
Key Requirements:
- •Prime all six sides: Prevents moisture intrusion from behind
- •Aluminum coil stock alternative: Consider pre-finished metal trim
- •Ventilation: Don't paint over soffit vents (blocks airflow)
- •Back-side sealing: Critical for fascia exposed to roof runoff
EPA Lead-Safe Renovation Rule (RRP)(40 CFR 745)
View StandardFederal requirements for disturbing lead paint in homes built before 1978. Contractors must be EPA-certified and follow lead-safe work practices when scraping, sanding, or removing old paint.
Key Requirements:
- •Pre-1978 homes: Assume lead paint present until tested
- •Certified renovators: EPA RRP certification required for contractors
- •Containment: Plastic sheeting, warning signs, restrict access
- •Cleanup: HEPA vacuum, wet cleaning, proper waste disposal
- •Documentation: Provide lead pamphlet, keep records 3 years
Standards Disclaimer: Standards and codes are subject to periodic updates. Always verify current requirements with local building authorities and professional engineers before beginning construction. Links provided are for reference only.
Climate Zone Paint Selection
UV exposure, temperature extremes, and moisture levels
Different climates require different paint formulations. UV-resistant paints for sunny areas, flexible paints for freeze-thaw zones, and mildew-resistant formulas for humid climates.
Regional Examples:
Temperature and Weather Restrictions
Application temperature limits vary by product and climate
Most exterior paints require surface temperatures between 50-90°F for proper curing. Cold weather formulas allow painting down to 35°F but cure more slowly.
Regional Examples:
VOC Regulations by State
Volatile Organic Compound limits restrict paint formulations
Some states limit VOC content in exterior paints to reduce air pollution. Low-VOC paints may have different application properties and coverage rates.
Regional Examples:
Historic District Requirements
Architectural review boards restrict colors and finishes
Properties in historic districts often face strict paint color and finish restrictions. Must use period-appropriate colors from approved palettes, sometimes requiring special lime-based paints.
Regional Examples:
HOA Color Restrictions
Homeowner Association design guidelines
Many HOAs restrict exterior paint colors to maintain neighborhood aesthetics. Approval process required before painting, with specific color palettes that must be followed.
Regional Examples:
Coastal and Hurricane Zone Requirements
Enhanced durability for salt air and high winds
Coastal properties need specialized paints resistant to salt spray, UV exposure, and high winds. More frequent repainting schedules recommended.
Regional Examples:
Wildfire Zone Restrictions
Non-combustible and fire-resistant coatings
Wildfire-prone areas may require or incentivize fire-resistant exterior coatings. Some areas mandate non-combustible siding within defensible space.
Regional Examples:
Lead Paint Requirements (Pre-1978 Homes)
EPA RRP Rule - Federal regulation
Properties built before 1978 likely contain lead paint. EPA requires certified contractors, containment procedures, and specific work practices when disturbing lead paint.
Regional Examples:
Before You Build
- •Contact your local building department for specific requirements
- •Verify frost line depths, wind zones, and seismic requirements for your area
- •Check if permits are required and schedule required inspections
- •Consult with a local contractor familiar with local codes
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.
🎨 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.
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🔧 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.