Quick Takeaway
To calculate paint: Total Wall Area = (2 × Length × Height) + (2 × Width × Height). Deduct 21 sq ft per door and 15 sq ft per window. Divide net surface area by 350 (sq ft coverage per gallon) and multiply by the number of coats (standard: 2 coats). One gallon covers approximately 350 to 400 square feet.
How to Calculate Paint for Any Room
Accurate paint estimation prevents mid-project store runs and saves money by avoiding excess paint cans. For smooth drywall, 1 gallon typically covers 350–400 sq ft. For textured walls, brick, or unprimed drywall, reduce the coverage estimate to 250–300 sq ft per gallon.
Standard Paint Coverage & Coats by Surface
| Wall / Surface Type | Coverage per Gallon / Liter | Recommended Coats |
|---|---|---|
| Smooth Drywall (Previously Painted) | 350 – 400 sq ft / gal (9 – 10 m²/L) | 2 Coats |
| New / Raw Drywall | 250 – 300 sq ft / gal (6 – 7.5 m²/L) | 1 Primer + 2 Paint Coats |
| Textured Walls / Stucco | 200 – 250 sq ft / gal (5 – 6 m²/L) | 2 to 3 Coats |
| Ceilings (Flat White) | 350 – 400 sq ft / gal (9 – 10 m²/L) | 1 to 2 Coats |