Paint Calculator
Sources & Methodology
Gallons = Total Area / 350 sq ft per gallonCoverage rate varies by paint type and surface
Standard coverage: 350-400 sq ft/gallon. Textured surfaces need more.
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Interior Painting Cost Guide on CostOnce.comHow to Use the Paint Calculator
Our paint calculator estimates how many gallons of paint you need based on your room dimensions and number of coats. We automatically deduct 15% for doors and windows to give you a realistic estimate. Need to measure your walls? Use our square footage calculator first.
Coverage Assumptions
We assume standard coverage of 350 square feet per gallon, which is typical for quality interior latex paint on primed surfaces. Textured walls, dark colors covering light, or unprimed surfaces may require more paint.
Tips for Better Results
- Two coats are recommended for best coverage and durability
- Always buy slightly more than calculated to ensure color consistency
- For ceilings, calculate separately using length × width
- Primer may be needed for new drywall, stains, or dramatic color changes
Related Room Renovation Projects
Planning a full room renovation? You may also need our tile and flooring calculator for new floors, drywall calculator for wall repairs, or lumber calculator for trim and molding. Calculate your project percentage complete to track progress.
Professional Considerations
For high ceilings, intricate trim work, or special finishes like faux painting, consider consulting a professional painter for accurate time and material estimates.
Frequently Asked Questions
A 12x12 room with 8-foot ceilings has about 384 square feet of wall space. After deducting 15% for doors and windows, you need approximately 326 square feet of coverage. One gallon covers 350-400 sq ft, so one gallon is sufficient for one coat, or two gallons for two coats.
One gallon of quality interior paint typically covers 350-400 square feet on smooth, primed surfaces. Coverage decreases to 250-300 square feet on textured walls, porous surfaces, or when covering dark colors with light paint.
Two coats are recommended for best results, especially when changing colors dramatically, painting over repairs, or using low-sheen finishes. One coat may suffice when repainting the same color with quality paint on smooth, previously painted surfaces.
Multiply length by width to get square footage. A 12x14 foot ceiling equals 168 square feet. Divide by 350 (coverage per gallon) to get gallons needed. For this ceiling, 0.48 gallons for one coat, so buy 1 gallon for two coats.
Flat paint hides imperfections but is hard to clean - good for ceilings and low-traffic areas. Eggshell has slight sheen and is washable - ideal for living rooms and bedrooms. Semi-gloss is durable and moisture-resistant - best for kitchens, bathrooms, and trim.
Latex paint typically needs 2-4 hours between coats in normal conditions (50-85 degrees F, moderate humidity). Oil-based paint requires 24 hours. Always check the can for specific recommendations, and wait longer in cold or humid conditions.
Primer is recommended for new drywall, bare wood, stains, dramatic color changes (dark to light), or glossy surfaces. Many quality paints include primer, but separate primer provides better adhesion and coverage for challenging surfaces.
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