Do I always need two coats of paint?

Paint Calculator - How Many Gallons of Paint Do I Need? (2026)

Calculate how many gallons of interior or exterior paint you need. Automatically accounts for ceiling height, doors, windows, and 1 or 2 coats of paint.

⚙️ Configuration & Inputs

Room Perimeter (Total Wall Length)2 × (Length + Width)

Ceiling HeightStandard 8 ft or 9 ft

Doors (-21 sq ft)

Windows (-15 sq ft)

Number of Coats

📊 Results & Analysis

Paint Required

2 Gallons

Covers 726 sq ft of wall surface

Gross Wall Area	450 sq ft
Window & Door Deductions	-87 sq ft
Net Surface Area (1 Coat)	363 sq ft
Total Area to Paint (2 Coats)	726 sq ft
Exact Decimal Gallons	2.07 Gallons

How to Estimate Paint Quantities

As a general rule, one gallon of quality interior paint covers approximately 350 to 400 square feet of smooth wall surface. Subtract 21 sq ft for each standard door and 15 sq ft for each window.

Frequently Asked Questions

Yes. A second coat provides uniform color depth, hides substrate imperfections, and extends the paint's durability by several years.