MaterialQuant

Paint Calculator

How much paint to buy for one room or a whole floor. Deduct doors and windows, set coats and manufacturer coverage, and get gallons in whole containers.

Wall paint, ceiling paint and primer each get their own order line. Named product coverage ranges remain visible; custom coverage works with your chosen paint.

Measure the rooms once

Walls, ceiling and openings. Every material below reads these.

Length and width of the floor, and the wall height.

Doors & windows entered once — each material decides how to treat them

What are you calculating?

Pick one or several. Each reads the rooms above.

Paint

On by default: an opening has no wall surface to paint. Turning this off adds margin; it does not calculate door or trim paint.

Wall paint

Data sheet 101.02A: 350–400 sq. ft. per gallon at 4 mils wet, 1.4 mils dry.

Two coats is the manufacturers' recommendation — Benjamin Moore: two coats for full color development, two on bare surfaces; previously painted surfaces can take 1 or 2.

Primer

Choose primer from your product's preparation instructions. SuperPaint lists two self-priming coats on drywall or a separate primer followed by two finish coats. Surface condition and color changes can require a different system.

Buying

Gallons are bought at the low end of the manufacturer's coverage range, rounded up to whole containers with the least paint left over.

%

None by default — no manufacturer publishes one.

Prices

Wall paint

How much paint do I need?

For a rectangular room, gross wall area is 2 × (length + width) × height. Subtract the doors and windows you choose to exclude. Multiply the resulting area by the coat count, then divide by coverage per gallon. Apply your optional extra percentage before rounding to containers. Ceiling area is length × width and is calculated on its own paint line.

Coverage is product-specific

The presets include SuperPaint Interior Flat at 350–400 ft² per gallon and Regal Select Matte at 400–450. The purchase calculation uses the lower coverage figure; results also show the requirement at the higher figure. Texture, porosity and application affect yield. Use Custom for another product or a project-specific coverage figure. All gallons here are US gallons.

Worked example: two coats on bedroom walls

For a 12 × 10 × 8 ft room, walls total 352 ft². A 21 ft² door and two 12 ft² windows leave 307 ft². Two coats cover 614 ft². At 350 ft² per gallon, that is 1.754 gallons before extra. With 1-gallon and 5-gallon containers enabled, the purchase is two 1-gallon containers. Turning on ceiling paint adds a separate 120 ft² surface; it does not silently use the wall paint.

Containers and cost

Enable the container sizes available in your product and color. The calculator first minimizes leftover paint, then the number of containers. It is not a cheapest-price optimizer. Enter prices for the container sizes used in each line to get that line’s cost. Missing prices are not treated as free materials.

Primer, coats and extra

Two finish coats and one optional primer coat are editable starting choices associated with the listed systems. Follow the selected manufacturer’s preparation requirements. Extra starts at zero; add your own allowance for application losses or touch-up stock. A primer is not a replacement for cleaning or repairing the substrate.

Questions before you order

Should I deduct doors and windows?

Yes for wall paint, unless you deliberately want extra margin. Deduction is enabled by default. Door faces, trim and frames need their own appropriate coating; disabling the deduction does not calculate them separately.

Can I calculate just ceiling paint?

Yes. Turn off walls and enable ceiling paint. The ceiling product, coats and prices are independent from the wall settings.

Can I combine rooms with different colors?

Each coating line assumes one product and color across its selected rooms. Use separate saved project links for different finishes so container rounding does not incorrectly combine paint that cannot be shared.

Product sources and assumptions

Presets describe named products, not every product in that material family. Confirm current label coverage, sizes, availability and preparation instructions. Custom values let you use the product you are buying. Prices are entered by you.

Paint

See methodology and sources for the assumptions behind the rest of your project.

Use the same measurements

Working outside too? Open the Hardscaping Calculator or Landscaping Calculator for those material orders.