Calculate exactly how much paint you need for your room. No more guessing or extra trips to the store.
Standard door = 20 sq ft
Standard window = 15 sq ft
Buying the right amount of paint saves money and ensures color consistency across your project. Here's everything you need to know about calculating paint quantities.
Gallons needed = (Wall area × Number of coats) ÷ 350 sq ft + 10%
One gallon of paint covers approximately 350-400 square feet. We use 350 sq ft for conservative estimates, then add 10% for waste, touch-ups, and surface variations.
| Situation | Coats Needed |
|---|---|
| Same color refresh | 1 coat (maybe) |
| Similar colors (white to off-white) | 1-2 coats |
| Different color (standard) | 2 coats (recommended) |
| Light over dark color | 2-3 coats + primer |
| Dark or bold colors (red, navy) | 3+ coats |
| New drywall | Primer + 2 coats |
Before painting, it helps to have an accurate floor plan of your room. Use Room Sketch 3D to draw your room to scale, note where doors and windows are located, and export a plan with exact dimensions to reference during your project.
One gallon of paint typically covers 350-400 square feet. Calculate your wall area (perimeter × height), subtract doors (20 sq ft each) and windows (15 sq ft each), then divide by 350. Our calculator does this automatically and accounts for the number of coats you need.
Most rooms need 2 coats for even coverage. Use 1 coat if painting the same color or using paint+primer. Use 3 coats when covering dark colors with light ones, or for bold/deep colors. Primer is recommended when painting new drywall or covering stains.
Yes, buy 10-15% more than calculated for touch-ups and to account for surface porosity. Keep leftover paint (properly sealed) for future touch-ups. Our calculator includes this buffer in the recommendation.
Slightly. Flat/matte paints may need more coats to achieve even coverage compared to satin or semi-gloss. However, the square footage coverage per gallon is similar. Choose sheen based on the room's function: flat for ceilings, eggshell for living areas, semi-gloss for kitchens/baths.
