Architectural Paint Calculator
Calculate paint gallons, commercial 5-gallon pails, and coverage requirements with opening deductions and real-time 3D cutaway room visualization.
Transparent Paint & Surface Calculation Breakdown
Perimeter = (14 + 12) × 2 = 52 ft
Gross Area = 52 × 9 = 468 sq ft
1 Doors (21) + 2 Windows (30)
Net Wall Surface = 468 - 51 = 417 sq ft
417 × 2 coats ÷ 350 sq ft/gal
= 3 Gallons total required.
How to Calculate Paint for Interior Walls and Ceilings
Estimating interior architectural coatings requires determining the net paintable drywall or plaster surface area. One standard U.S. gallon of interior latex or acrylic paint covers approximately 350 to 400 square feet on smooth primed drywall (or 8.5 to 10 square meters per liter). Unprimed fresh drywall, textured ceilings, or stucco absorb more coating, reducing spreading rate to approximately 250 to 300 sq ft/gallon.
Why Two Coats Are Standard Practice
Two coats provide uniform film thickness (mil build), conceal underlying patches or contrasting pigment, and produce true manufacturer sheen (eggshell, satin, semi-gloss). While some commercial paints are advertised as "one-coat coverage," professional painting contractors consistently specify two finish coats over primer for warranty compliance and scrub resistance.
Standard Opening Deduction Allowances
Architectural takeoffs deduct 21 sq ft (2.0 m²) for each standard interior door (3'-0" × 7'-0") and 15 sq ft (1.4 m²) for each standard double-hung or casement window (3'-0" × 5'-0"). For expansive picture windows or sliding patio doors, measure actual dimensions and deduct manually.