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Paint Calculator

Paint Calculator

Enter a room's dimensions, openings, number of coats, and product coverage. The project plan estimates paint and primer gallons, covered surface area, supplies, labor, and three cost scenarios.

22-calculator project library Reviewed 2026-07-25Calculations run privately in your browser

Enter project details

Example values are prefilled

Room dimensions

Room length

Measure wall to wall.

Room width

Wall height

Standard doors

Each door deducts 21 sq ft.

Standard windows

Each window deducts 15 sq ft.

Include ceiling

Paint assumptions

Finish coats

coats

Coverage per gallon

sq ft

Use the label value for your paint.

Waste and touch-up allowance

Include one primer coat

Paint price per gallon

Primer price per gallon

Labor per paintable sq ft

Location and tax assumptions

The location factor adjusts labor only. Replace all default prices with actual local quotes before purchasing.

Local labor-cost factor

A coarse planning adjustment—not a ZIP-code quote.

Sales tax on materials

Enter the tax rate that applies to taxable materials.

All default prices are editable examples. Cost scenarios vary the entered plan; they do not represent bids or guarantees.

How to use this paint calculator

Estimate wall and ceiling paint, primer, supplies, labor, waste, and total project cost for a room.

Formula

Wall area = 2 × (length + width) × height − door area − window area. Paint gallons = finish-coat area × (1 + waste %) ÷ labeled coverage, rounded up.

Worked example

Example: A 12 × 10 ft room with 8 ft walls, one door, two windows, two coats, and a ceiling has 421 sq ft of paintable surface before multiplying by coats. At 375 sq ft per gallon plus 10% waste, the plan rounds up to whole gallons.

Accuracy and limitations

Paint coverage changes with color, surface texture, application method, and product. Use the manufacturer's coverage and buy enough for color consistency.

Frequently asked questions

Should I subtract doors and windows?

Yes for a tighter estimate. This calculator uses 21 sq ft per standard door and 15 sq ft per standard window.

Why add waste?

Waste covers roller loading, spills, touch-ups, and leftover paint for later repairs.

Does the estimate include trim?

No. Calculate trim separately because enamel coverage, coats, and pricing usually differ from wall paint.