Paint Calculator
Enter Room Details
About Paint Calculator
How Much Paint Do You Need?
Buying the right amount of paint saves money and multiple trips to the store. One gallon of paint typically covers approximately 350-400 square feet of wall space with one coat. Most painting projects require two coats for proper coverage, which effectively halves the coverage per gallon. The actual coverage depends on paint quality, wall texture, surface porosity, and color change (going from dark to light requires more paint). This calculator takes all these factors into account to give you an accurate estimate.
How the Calculation Works
The calculator computes total wall area using the formula: Wall Area = Perimeter x Height. It then subtracts areas for doors (approximately 21 sq ft each) and windows (approximately 15 sq ft each). The net paintable area is divided by coverage rate per gallon and multiplied by number of coats. A 10% waste factor is added for trim, touch-ups, and roller absorption.
How to Use This Calculator
Enter room length, width, and wall height. Specify the number of doors and windows. Select how many coats you plan to apply and whether you are also painting the ceiling. The calculator shows total paintable area, gallons needed (rounded up to nearest purchasable quantity), and estimated cost if you enter the price per gallon.
Frequently Asked Questions
How much does one gallon of paint cover?
One gallon covers approximately 350-400 sq ft with one coat on smooth surfaces. Textured walls, raw drywall, or porous surfaces may reduce coverage to 250-300 sq ft per gallon.
Do I always need two coats?
Two coats provide the best results for durability and even color. You might get away with one coat when painting over a similar color using premium paint with built-in primer. Dark-to-light color changes may need three coats.
Should I buy extra paint?
Yes. Buy 10-15% more than calculated for touch-ups, roller waste, and future repairs. Keep leftover paint sealed for touch-ups later. Most stores accept returns of unopened gallons.
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