Paint & Walls

Paint Calculator

Estimate gallons of paint for room walls and ceilings, including coats, doors, windows and optional waste.

Room Details

Room Length (ft)

Room Width (ft)

Wall Height (ft)

Coats123

Doors

Windows

Include ceiling

Coverage per gallon

Waste Allowance0510

Price per gallon (optional)

Recommended Paint

2 gallons

For 2 coats with 5% waste

Paintable Area300 ft²

Total Coat Area600 ft²

Exact Gallons1.80 gal

Estimated Cost—

Paint coverage varies with surface texture, color change, primer and product. Always check the manufacturer's stated coverage.

How Much Paint Do I Need?

The calculator estimates the paintable wall area from your room dimensions, subtracts approximate door and window areas, and then multiplies the result by the number of coats.

How the Paint Calculation Works

For a rectangular room, wall area is estimated from the perimeter:

Wall Area = 2 × (Length + Width) × Height

Door and window areas are then subtracted. If you select the ceiling option, the ceiling area is added.

Coverage varies: Paint coverage depends on the product, surface texture, color change, primer, application method and porosity of the surface.

One Coat vs Two Coats

A single coat may be sufficient for some refresh projects with similar colors and good existing surfaces. Major color changes, new drywall or uneven surfaces often require additional coats or primer.

Example Paint Calculation

Imagine a 12 ft by 10 ft room with 8 ft walls, one door and two windows.

The total wall area is approximately 352 ft² before subtracting openings. After subtracting the approximate openings, the paintable area is about 301 ft².

For two coats, this becomes roughly 602 ft² of coat coverage before waste.

Should I Buy Extra Paint?

A small extra allowance can be useful for touch-ups and minor application losses. If matching color later may be difficult, keeping a small amount of the original paint can also be useful.

Frequently Asked Questions

How much area does one gallon of paint cover?

Coverage varies by product. Many paints list a coverage range on the label. Enter the manufacturer's stated coverage into the calculator for a better estimate.

Should I include the ceiling?

Only select the ceiling option if you plan to paint it with the same estimated coverage assumptions.

Do I need primer?

Primer needs depend on the surface, stain blocking, material and color change. Follow the paint manufacturer's recommendation.

Planning estimate: Actual coverage varies. Always check the paint manufacturer's instructions and coverage information.