How much paint do I need?

Calculate total wall area, subtract doors and windows, multiply by number of coats, then divide by paint coverage (typically 350 sq ft per gallon). Formula: Paint = (Total Area - Deductions) × Coats ÷ Coverage

What is standard paint coverage?

Most interior and exterior paints cover 350-400 sq ft per gallon. Premium paints may cover up to 450 sq ft/gallon. Always check your paint specification for exact coverage.

How many coats should I apply?

Typically 2 coats for interior walls, 1-2 coats for ceilings, and 1-2 coats for exterior surfaces. Use more coats for color changes or darker colors.

Paint Calculator

Calculate how much paint you need for your project. Enter wall dimensions, number of coats, and deductions for doors and windows.

Enter wall dimensions, number of coats, and door/window deductions to calculate paint needed.

Paint estimationInterior paintingProject budgeting

Wall Height (ft)

Wall Width (ft)

Number of Walls

Number of Coats

Door/Window Deductions (sq ft)

Coverage (sq ft/gal)

Formula

Total Area = Height × Width × Number of Walls | Net Area = Total Area - Deductions | Paint = (Net Area × Coats) ÷ Coverage per Gallon

Calculate total wall surface area, subtract areas for doors and windows, then multiply by number of coats. Divide by paint coverage (typically 350 sq ft per gallon for standard paint) to get gallons needed.

Worked Example

Room: 9 ft height, 12 ft width, 4 walls, 2 coats, 100 sq ft deductions (doors/windows), 350 sq ft/gal coverage.

Total area = 9 × 12 × 4 = 432 sq ft

Net area = 432 − 100 = 332 sq ft

Area to coat = 332 × 2 = 664 sq ft

Paint needed = 664 ÷ 350 = 1.9 gallons (8 quarts)

Purchase 2 gallons of paint to ensure sufficient coverage with 2 coats.

Frequently Asked Questions

When to use this calculator

→Estimating paint quantity for interior or exterior projects
→Getting accurate quotes from painters with material estimates
→Budgeting for paint and supplies including multiple coats
→Comparing costs across different paint brands and qualities

Paint coverage and types

Standard Interior

Coverage: 350 sq ft/gal • Cost: Budget-friendly

Interior walls, common rooms

Premium Interior

Coverage: 400 sq ft/gal • Cost: Mid-range

Higher quality, better durability

Exterior Paint

Coverage: 350-400 sq ft/gal • Cost: Varies

Weatherproof, UV resistant

Primer

Coverage: 300-350 sq ft/gal • Cost: Lower

Base coat, stains, color changes

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Important Note

These are estimates for planning. Actual material needs may vary due to site conditions, cuts, and waste. Verify quantities with your contractor or supplier before ordering.