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Room Paint Calculator

Use this room paint calculator when you know room dimensions in feet or meters and want a quick gallons-and-cost estimate.

Method and assumptions documentedFree toolSource note included

Live calculator

Room paint

Paintable area292 sq ft

352 sq ft / 32.7 sq m before openings.

Paint needed1.75 gallons

1.67 raw gallons, rounded to quarts.

Estimated paint cost$66.50

Rounded gallons multiplied by price per gallon.

Material estimates need field measurements and a waste allowance. Supplier coverage, cuts, breakage, compaction, and local installation requirements can change the order quantity.

Quick answer

Room Paint Calculator: what it calculates

Room Paint Calculator estimates gallons and cost for a single room from room dimensions, selected walls, openings, coats, coverage, and paint price.

ResultRoom paint needed
InputsFeet or meters, Room length, Room width, Wall height, Walls, Coverage
FormulaRoom paint formula

Formula

Room paint formula

Paintable area = selected wall perimeter x height - doors/windows; gallons = area x coats / coverage

Use feet/square feet or meters/square meters. Coverage varies by product, surface texture, primer, color change, and application method.

How to use

Steps

  1. Choose feet or meters for the room measurements.
  2. Enter room length, width, and wall height.
  3. Choose how many walls are being painted.
  4. Subtract estimated door and window area in square feet or square meters.
  5. Enter coats, coverage per gallon, and price per gallon.

Example

Sample calculation

Room12 ft x 10 ft x 8 ft
Metric equivalent3.66 m x 3.05 m x 2.44 m
Doors/windows60 sq ft / 5.57 sq m
Two coatsAbout 1.67 gallons
Rounded buy amount1.75 gallons

Calculator use

Best for

  • Estimating paint for a single room when you know room length, width, wall height, openings, coats, and coverage.
  • Checking one-wall, two-wall, three-wall, or full-room painting scenarios before buying paint.
  • Comparing paint cost when coverage per gallon or price per gallon changes.
  • Getting a quick room-specific estimate before using the broader paint calculator for multiple rooms.

Before relying on it

Check first

  • Counting all walls when only an accent wall or selected walls will be painted.
  • Leaving out doors, windows, closets, trim, ceilings, repairs, primer, or strong color changes.
  • Treating rounded gallons as the exact purchase size when paint is sold in specific container sizes.
  • Using room dimensions without checking wall texture, patching, stains, or product coverage on the can.

Details

What to know before using the result

Wall perimeterRoom dimensions

The calculator estimates full room perimeter in feet or meters, then scales it by the number of walls selected.

OpeningsDoors and windows

Subtracting openings keeps the estimate from overstating paintable wall area.

Rounded gallonsQuarter-gallon planning

The calculator rounds up to the nearest quarter gallon for planning, but actual purchase sizes depend on the paint product.

Source notes

References used for this calculator

Sherwin-WilliamsPaint calculator guidance notes that one gallon typically covers about 350 to 400 square feet, depending on surface and coverage.

Benchmarks

How to read the result

One coat: Refresh only.

May work when color and surface are similar and paint coverage is strong.

Two coats: Common interior plan.

Often used for better coverage, color changes, or touchy surfaces.

350 - 400 sq ft: Typical gallon range.

Use the product label when available because coverage varies.

Calculator accuracy

Methodology and assumptions

Formula

Paintable area = selected wall perimeter x height - doors/windows; gallons = area x coats / coverage

Inputs used

Feet or meters, Room length, Room width, Wall height, Walls, Coverage

Limitations

Home-material calculators estimate quantity and cost from visible dimensions and coverage assumptions. They do not replace field measurement, installer guidance, structural design, permits, or code review.

Review record

Catalog QA baseline on June 6, 2026. This date marks the catalog-wide automated and editorial QA baseline, not a tool-specific expert review.

Cite this page

Toolkit Shelf. Room Paint Calculator. https://toolkitshelf.com/tools/room-paint-calculator

FAQ

Common questions

How do I calculate paint for a room?

Estimate wall area from room perimeter and wall height, subtract doors and windows, multiply by coats, then divide by paint coverage per gallon. You can use feet/square feet or meters/square meters.

How many coats should I enter?

Two coats are common for interior walls, but one coat may work for a light refresh and primer may be needed for new drywall or strong color changes.

Should I round up paint?

Yes. Rounding up helps avoid running short and leaves extra for touchups.

Why should I add a material buffer?

Cuts, waste, damaged pieces, uneven surfaces, pattern matching, delivery limits, and field measurements can all make the exact calculated amount too low.

Can this replace a contractor quote?

No. Use it for planning quantities and budgets. Labor, permits, code, site conditions, disposal, access, and contractor scope can change the real project cost.