Fixed imperial example
How much paint for a 12 × 12 ft room?
Four 12 × 8 ft walls total 384 ft². Subtracting one 3 × 7 ft door leaves 363 ft²; two coats create 726 coated square feet.
Measure walls and subtract openings
Enter each 12 × 8 ft wall as a surface and the 3 × 7 ft door as an opening. PaintCalc subtracts 21 ft² from 384 ft². Add windows or other rectangular openings only when you do not plan to paint them.
Apply coats and the label value
Two coats make 726 coated square feet. At an entered coverage of 350 ft²/US gal, the exact requirement is about 2.074 US gal. With 1 US gal containers, the purchase count rounds up to three.
Frontend-only calculator