Find out how many gallons of paint you need for any room.
Estimating paint quantity involves three steps. First, calculate the total wall area by adding the perimeter of the room (two lengths plus two widths) and multiplying by the wall height. Second, subtract non-paintable areas like doors (about 21 sq ft each for a standard 3x7 ft door) and windows (about 15 sq ft each for a standard 3x5 ft window). Third, multiply the paintable area by the number of coats, then divide by the coverage rate of your paint (typically 350 sq ft per gallon for smooth surfaces). Always round up to the nearest full gallon, and consider buying an extra quart for touch-ups.
Smooth, primed walls: 350-400 sq ft per gallon. This is the standard coverage quoted on most paint cans. Textured or rough surfaces: 250-300 sq ft per gallon. The texture absorbs more paint and creates more surface area. New drywall: 300-350 sq ft per gallon for the first coat (primer), and standard coverage for subsequent coats. Always prime new drywall before painting. Brick and masonry: 150-200 sq ft per gallon due to the extremely porous and uneven surface. These surfaces often require a masonry-specific primer and may need an extra coat. The Square Footage Calculator can help measure irregular room shapes.
Most paint jobs require two coats for a professional finish. One coat may be enough if you are repainting with the same or very similar color and the existing paint is in good condition. Two coats are necessary when changing colors (especially going lighter), painting over a dark color, using a new color for the first time, or working with certain paint finishes like flat or matte that show roller marks more easily. Three coats may be needed when going from a very dark color (like navy or black) to a very light color (white or pastel), or when covering stains that bleed through primer.
Interior paint prices range widely. Budget paint runs $20-30 per gallon, mid-range options (Behr, Valspar, Glidden) cost $30-50 per gallon, and premium paints (Benjamin Moore, Sherwin-Williams, Farrow and Ball) run $50-80+ per gallon. This calculator estimates cost at $40 per gallon as a mid-range baseline. Higher-quality paints generally provide better coverage, requiring fewer coats, and last longer before needing repainting. For a single bedroom (12x14 ft), expect to spend $80-160 on paint for walls only with two coats.
Buy 10-15% extra beyond the calculated amount for touch-ups, waste, and uneven surfaces. Keep leftover paint sealed tightly for future touch-ups. Check the can label for the specific coverage rate, as it varies by brand and finish. Flat and matte finishes typically cover slightly more than satin or semi-gloss. Ceiling paint is usually thicker and covers slightly less (300-350 sq ft per gallon). The Concrete Calculator helps estimate materials for other home projects.
Standard coverage is 350-400 square feet per gallon on smooth, previously painted walls with two coats. Textured walls (knockdown, orange peel, popcorn) drop that to 250-300 sq ft. New drywall absorbs more on the first coat. Going from a dark color to a light one usually needs three coats or a tinted primer.
This calculator accounts for wall area, doors, windows, surface type, and number of coats. It errs slightly high because running out mid-project means a trip to the store and potentially a color mismatch between batches. Always keep at least a quart for future touch-ups. For a complete painting planning guide, see how much paint you need.