Gallon

What is a Gallon?

A gallon is a unit of liquid measurement equal to 4 quarts, 8 pints, or 128 fluid ounces. In construction and contracting, gallons are the standard unit for measuring and pricing liquid materials like paint, stain, sealers, adhesives, and chemical treatments.

Understanding gallon coverage helps contractors accurately estimate material needs and costs for projects.

Common Materials Sold by the Gallon

Paints and Coatings

• Interior paint: Latex and oil-based wall paints
• Exterior paint: House paints and trim coatings
• Primer: Sealing and preparation coatings
• Specialty coatings: Anti-rust, epoxy, textured finishes

Stains and Sealers

• Wood stain: Interior and exterior wood coloring
• Concrete sealer: Protection for driveways and walkways
• Deck stain: Semi-transparent and solid color stains
• Masonry sealer: Brick and stone protection

Adhesives and Chemicals

• Construction adhesive: Liquid bonding agents
• Roof coatings: Protective and repair coatings
• Waterproofing: Foundation and basement sealers
• Cleaning solutions: Concrete cleaners, prep solutions

Paint Coverage Standards

Interior Paint Coverage

• Standard coverage: 350-400 square feet per gallon
• Premium paint: 400-450 square feet per gallon
• Textured surfaces: 250-300 square feet per gallon
• Smooth surfaces: 400-500 square feet per gallon

Exterior Paint Coverage

• Siding (smooth): 350-400 square feet per gallon
• Siding (textured): 250-350 square feet per gallon
• Stucco: 200-300 square feet per gallon
• Brick/masonry: 200-250 square feet per gallon

Primer Coverage

• Standard primer: 300-400 square feet per gallon
• High-build primer: 200-300 square feet per gallon
• Specialty primers: Varies by product (check label)

Calculating Paint Needs

Basic Formula

Total Square Feet ÷ Coverage per Gallon = Gallons Needed

Wall Area Calculation

1. Measure room perimeter: Add all wall lengths
2. Multiply by height: Perimeter × ceiling height
3. Subtract openings: Doors (~20 sq ft), windows (~15 sq ft each)
4. Divide by coverage: Total area ÷ coverage per gallon

Example Calculation

Room: 12' × 15' with 9' ceilings, 2 windows, 1 door

• Perimeter: (12 + 15 + 12 + 15) = 54 feet
• Wall area: 54 × 9 = 486 square feet
• Subtract openings: 486 - 20 - 30 = 436 square feet
• Paint needed: 436 ÷ 400 = 1.1 gallons (order 2 gallons)

Coverage Variables

Surface Factors

Smooth surfaces: Maximum coverage per gallon Rough textures: Reduced coverage due to increased surface area Porous materials: May require additional coats or primer

Application Method

Brush application: Typically uses more paint than rolling Roller application: Standard coverage rates apply Spray application: May use 10-20% more material

Number of Coats

• Single coat: Rare, usually only over similar colors
• Two coats: Standard for most projects
• Three coats: Dark to light color changes, new construction

Stain and Sealer Coverage

Wood Stain Coverage

• Smooth lumber: 150-200 square feet per gallon
• Rough lumber: 100-150 square feet per gallon
• Decking: 200-300 square feet per gallon
• Fencing: 150-250 square feet per gallon

Concrete Sealer Coverage

• Smooth concrete: 200-400 square feet per gallon
• Broom finish: 150-300 square feet per gallon
• Exposed aggregate: 100-200 square feet per gallon

Container Sizes and Pricing

Standard Sizes

• Quart: 1/4 gallon (covers ~100 sq ft)
• Gallon: Standard size for most projects
• 5-gallon bucket: Bulk pricing, covers ~2,000 sq ft

Pricing Considerations

• Per-gallon cost decreases with larger container sizes
• Specialty products command premium pricing
• Color matching may require minimum quantities

Quality Factors Affecting Coverage

Paint Quality Levels

Economy paint: Lower coverage, may require more coats Standard paint: Advertised coverage rates typically apply
Premium paint: Often provides better coverage and fewer coats needed

Pigment Content

High-quality paints: Better hiding power and coverage Light colors: Generally provide better coverage than dark colors Deep base paints: May require additional coats for full coverage

Ordering Tips

Account for Waste

• Touch-ups: Order 10-15% extra for future touch-ups
• Application waste: Brushes, rollers, and spraying create waste
• Color consistency: Order all paint for project at once

Storage Considerations

• Shelf life: Most paints last 2-10 years when properly stored
• Temperature: Store in climate-controlled environment
• Mixing: Stir thoroughly before use, especially after storage

Common Mistakes

Underestimating Coverage: Rough or porous surfaces use more paint than smooth surfaces.

Forgetting Multiple Coats: Most projects require 2-3 coats for proper coverage.

Not Accounting for Touch-ups: Always order extra material for future maintenance.

Ignoring Surface Prep: Poor prep work increases paint consumption and reduces quality.