Calculate how much paint you need for your project. Enter room dimensions, subtract doors and windows, and get accurate estimates for gallons needed and total cost based on coverage rates and number of coats.
Standard door = 21 sq ft
Standard window = 15 sq ft
Typical: 300-400
Paint coverage is measured in square feet per gallon and varies significantly based on paint type, surface texture, and application method. Standard interior latex paint typically covers 350-400 square feet per gallon on smooth, primed surfaces. However, porous surfaces like bare drywall, textured walls, or rough wood can reduce coverage to 250-300 square feet per gallon.
The calculator uses 350 square feet per gallon as a conservative default, ensuring you have enough paint to complete your project. Professional painters often calculate at 300-325 square feet per gallon to account for real-world conditions like surface absorption, roller texture, and application technique.
Different paint formulations have different coverage rates. Understanding these differences helps you choose the right product and calculate accurate quantities.
| Paint Type | Coverage (sq ft/gal) | Best For | Typical Coats |
|---|---|---|---|
| Flat/Matte Interior | 400-450 | Ceilings, low-traffic walls | 2 |
| Eggshell/Satin Interior | 350-400 | Living rooms, bedrooms | 2 |
| Semi-Gloss Interior | 350-400 | Kitchens, bathrooms, trim | 2 |
| Exterior Latex | 250-350 | Siding, stucco, brick | 2-3 |
| Primer | 200-300 | Bare surfaces, stain blocking | 1 |
| Ceiling Paint | 350-400 | Ceilings (flat finish) | 1-2 |
Properly primed walls provide the best coverage efficiency. Primer seals the surface, creates uniform absorption, and allows topcoat to spread evenly. You'll typically achieve the manufacturer's stated coverage rate on primed surfaces.
Coverage: 350-400 sq ft/gallon for most interior paints
Unpainted drywall is highly porous and absorbs significantly more paint. The first coat acts partially as a primer, requiring 30-40% more paint than primed surfaces. Always prime bare drywall for best results.
Coverage: 250-300 sq ft/gallon without primer
Orange peel, knockdown, and popcorn textures increase surface area by 20-50% compared to smooth walls. Deep textures trap paint in valleys and require more material to achieve uniform coverage and color saturation.
Coverage: 250-325 sq ft/gallon depending on texture depth
Painting over existing paint in good condition provides the most efficient coverage. The sealed surface doesn't absorb paint, allowing it to spread further. Color changes may require additional coats for full coverage.
Coverage: 375-425 sq ft/gallon for similar colors
Painting white over beige, or light blue over light gray typically requires 2 coats for complete coverage. The similar color values allow good hiding with standard application.
Covering light walls with dark colors (navy, charcoal, deep red) usually requires 2-3 coats. Dark paints have less hiding power and the light base color can show through thin spots.
This is the most challenging scenario. Dark colors bleed through light paint easily. Use a stain-blocking primer first, then apply 2-3 coats of your light color. Without primer, expect 3-4 coats minimum.
Vivid reds, oranges, yellows, and other highly saturated colors often require 3 coats regardless of the base color. These pigments have lower opacity and need multiple applications for uniform color depth.
Purchase 2 gallons. You'll have some left over for touch-ups, which is ideal for future repairs.
Purchase 4 gallons. Consider buying a 5-gallon bucket if available—it's often more economical and ensures color consistency.
Purchase 1 gallon. Dark colors over light bases require extra coats. Consider tinting your primer to a mid-tone gray to reduce topcoat requirements.
Purchase 2 gallons of ceiling-specific paint. Ceiling paint is formulated to minimize drips and spatters, making application easier overhead.
Always purchase 10-15% more paint than calculated. You'll need it for touch-ups after moving furniture back, and paint batches can vary slightly in color. Having extra from the same batch ensures perfect matches for future repairs.
Rollers use less paint than sprayers but more than brushes. If spraying, increase your estimate by 20-30% to account for overspray. High-quality rollers with proper nap thickness (3/8" for smooth walls, 1/2" for light texture) optimize coverage.
Using primer on bare surfaces or dramatic color changes saves money overall. One coat of primer plus two coats of paint covers better and costs less than three or four coats of paint alone. Primer also improves paint adhesion and durability.
Reduce your coverage estimate by 20-30% for textured walls, bare wood, or porous surfaces like unfinished drywall or plaster. These surfaces absorb more paint and require additional material for uniform coverage and color saturation.
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