How Much Paint Do You Need?
Enter your room dimensions, pick your paint type, and get an instant material list with gallons, primer, and cost.
Paint Estimate
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How to Calculate How Much Paint You Need
Calculating paint is straightforward once you know the formula. Measure each wall's length and height, multiply to get the square footage, then subtract openings like doors (~21 sq ft each) and windows (~15 sq ft each).
One gallon of paint covers approximately 350–400 sq ft on smooth surfaces. Textured walls absorb more paint, reducing coverage to around 300 sq ft per gallon. New drywall (even primed) typically gets 350 sq ft per gallon.
Always plan for two coats— it's the industry standard for a quality finish. If you're covering a dark color with a light one, consider adding a coat of primer first.
Add a 10% waste factorto your final number. You'll lose paint to roller absorption, tray waste, and touch-ups. It's better to have a little extra than to run short mid-wall.
Pro tip: Buy all your paint at once from the same batch to avoid color variation between cans. Most paint stores will take back unopened gallons.
Frequently Asked Questions
How much paint do I need for a 12x12 room?
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A 12x12 room with 8-foot ceilings has about 384 sq ft of wall space. After subtracting a door and two windows (~51 sq ft), you have ~333 sq ft of paintable area. At 400 sq ft/gallon coverage, you need 2 gallons for two coats. Add 10% waste and buy 2 gallons.
How many square feet does a gallon of paint cover?
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One gallon of interior latex paint covers approximately 350-400 sq ft on smooth surfaces. Textured walls, porous surfaces, and dark-to-light color changes reduce coverage. For textured walls, plan on 300 sq ft per gallon.
Should I use one coat or two coats of paint?
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Two coats is the industry standard for a quality, even finish. One coat may work for touch-ups with the exact same color, but most jobs need two. If you're covering a dark color with a lighter one, you may need primer plus two topcoats.
How much does it cost to paint a room?
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DIY paint costs $100-$300 per room for materials (paint, primer, supplies). Professional interior painting costs $2-$6 per sq ft including labor. A typical 12x12 bedroom costs $200-$600 professionally painted.
Do I need primer before painting?
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You need primer when painting over new drywall, covering stains or odors, making a dramatic color change (dark to light or vice versa), or painting over a glossy surface. For repainting similar colors on previously painted walls, modern paint-and-primer combos can often skip the separate primer step.
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