Painting
Paint Calculator Calculator USA 2026
Estimate how many gallons of paint you need for any room, including doors, windows and the number of coats.
Unit system
Enter your measurements
Results
Paintable wall area
366 sq ft
Gallons required
2.1 gal
Quart cans (if <1 gal)
9
Calculation steps
- 1.Gross wall area = 52 × 8 = 416 sq ft
- 2.Openings = 1×20 + 2×15 = 50 sq ft
- 3.Paintable area = 416 − 50 = 366 sq ft
- 4.Gallons = (366 × 2) ÷ 350 = 2.09 gal
Includes a standard waste allowance. Verify with your supplier before ordering.
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Disclaimer: Estimates based on 2026 RSMeans USA data. Actual quantities vary by site conditions, waste and installer practices. Verify with your supplier or contractor before ordering.
How it works
- 1Add up the total wall length (perimeter) and ceiling height.
- 2Subtract standard 20 sq ft per door and 15 sq ft per window.
- 3Multiply by number of coats and divide by 350 sq ft coverage per gallon.
Formula
Gallons = (Wall Area − Openings) × Coats ÷ 350 sq ft per gallon
Worked example
A 12×14 room, 8 ft tall = 52 × 8 = 416 sq ft. Minus 1 door + 2 windows = 366 sq ft. Two coats ÷ 350 ≈ 2.1 gal.
Frequently asked questions
How much does a gallon cover?
Roughly 350 sq ft on primed drywall.
Do I need primer?
Yes on new drywall or drastic color changes.