Paint Calculator

Doors

Windows

Calculation Method

The paint calculator estimates the amount of paint needed using the following steps:

1. Wall area = 2 × (length + width) × height
2. Opening area = sum of all door and window areas (width × height × quantity)
3. Paintable area = wall area − opening area
4. Total area with coats = paintable area × number of coats
5. Paint needed = total area with coats ÷ coverage per gallon

Paint Coverage Guidelines

• Smooth walls: ~350–400 sq ft per gallon (32–37 m² per liter)
• Textured walls: ~250–300 sq ft per gallon (23–28 m² per liter)
• Rough/porous surfaces: ~200–250 sq ft per gallon (18–23 m² per liter)

Tips

• Always buy slightly more paint than the estimate to account for waste and touch-ups
• Dark colors over light surfaces typically require 2–3 coats
• Primer coats generally cover about the same area as paint
• Standard door size is approximately 3 × 7 ft (0.9 × 2.1 m)
• Standard window size is approximately 3 × 4 ft (0.9 × 1.2 m)