Paint Calculator

Estimate gallons, cost, and a printable shopping list for walls, ceilings, and trim.

Project details

Room length (ft)

Room width (ft)

Wall height (ft)

Doors (standard 3' x 7')

Windows (standard 3' x 4')

Coats

Waste (%)

Paint price per gallon (USD)

Include ceiling

Gallons needed 2.75 gallons

Estimated paint cost $119.97

Coverage used 350 sq ft per gallon

Item	Amount
Interior paint 963.6 sq ft adjusted area	3 gallons
Primer (optional) Use when changing color or painting bare drywall	3 gallons
Painter's tape	2 rolls
Drop cloths	1 each
Roller covers	4 each

Coverage varies by paint, surface texture, and application method. This calculator uses common interior estimates.

Walls	350 sq ft per gallon per coat
Standard door	21 sq ft opening deducted
Standard window	12 sq ft opening deducted
Waste	Added for spills, touch-ups, and uneven surfaces

How accurate is this calculator?

It gives a planning estimate. Always compare the result with the coverage number printed on your paint label.

Does it include ceilings?

Ceilings are optional. Check “Include ceiling” when the ceiling will be painted with the same paint.

Should I buy primer?

Primer is useful for bare drywall, stains, repairs, or major color changes.

Why round gallons up?

Paint is normally purchased by container size. Rounding up avoids running short near the end of the project.