Paint Calculator

How the Paint Calculator Works

This calculator helps you estimate how much paint you need for walls, rooms, and interior painting projects. It calculates total wall area, multiplies it by the number of coats, applies an optional waste factor, and determines how many gallons of paint you must buy.

Formulas Used

The calculator uses standard paint coverage formulas:

• Wall Area:
  (Length × Height × 2) + (Width × Height × 2)
• Total Area (with coats):
  Wall Area × Number of Coats
• Material Needed (with waste):
  Total Area × (1 + Waste % ÷ 100)
• Gallons Needed:
  Material Needed ÷ Coverage per Gallon

Example

Example for a 12 ft × 10 ft room, 8 ft height, 2 coats, 350 sq ft per gallon, and 10% waste:

Wall Area = (12 × 8 × 2) + (10 × 8 × 2) = 352 sq ft
Total Area (2 coats) = 352 × 2 = 704 sq ft
With 10% Waste = 704 × 1.10 = 774.4 sq ft
Gallons Needed = 774.4 ÷ 350 = 2.21 → 3 gallons