Skip to content
QuantoObra

Walls & Ceiling Paint Calculator

Painting the whole room? This version includes the ceiling by default, so you get one total for walls and ceiling — and the cans to buy.

Interior wallsWalls & ceilingExterior

Results update as you type.

Room

Measure by
ft
ft
ft
Doors
ft
ft
Windows
ft
ft
Add another room Pro

Paint

ft²/gal

Per coat. See the can.

%
$/gal

Price of a 1-gallon can. 5-gallon buckets are priced ~12% cheaper per gallon.

Advanced

Pro

Upgrade to Pro for multi-room projects, primer, separate ceiling paint, saved projects and branded PDF quotes.

Paint needed

2.51gallons

Paintable area
428 ft²
44 ft² openings deducted
Walls / ceiling
308 / 120
ft²
Recommended cans
3× 1-gal
Estimated cost
—
Add a price

Shopping list

  • 31-gallon can — paint

  • 1Roller, tray, brush & painter’s tape

    Recommended

Add prices below to see a cost estimate.

SaveProPDFPro

How we calculate

walls = 2 × (length + width) × height − doors − windows
ceiling = length × width
paint = (walls + ceiling) × coats ÷ coverage × (1 + waste %)

If you use a different paint on the ceiling (a Pro option), walls and ceiling are calculated separately with their own coverage and cans.

Painting walls and ceiling together

The ceiling of a rectangular room has the same area as the floor, so a 12 × 14 ft room has a 168 ft² ceiling — roughly half a gallon per coat. Including it in the same estimate makes sure you buy the right number of cans in one trip.

If walls and ceiling are the same colour (common with "ceiling white" walls in rentals), buy everything as one batch so the sheen and tint match. Otherwise, estimate them separately — ceiling paint is usually flat white and walls are eggshell or satin.

Frequently asked questions

How much paint do I need for a ceiling?

Ceiling area is simply length × width. A 12 × 12 ft ceiling is 144 ft²; two coats at 400 ft² per gallon need about 0.8 gallons — buy one gallon. Flat ceiling paints often cover a little more than wall paint.

Can I use wall paint on the ceiling?

You can, but dedicated ceiling paint is flatter (hides imperfections), more viscous (less spatter overhead) and usually cheaper. Pro users can set a separate coverage and price for ceiling paint.

Should I paint the ceiling or walls first?

Ceiling first. Drips and roller spatter land on the walls, which you paint afterwards, and you can cut in the wall colour cleanly against the finished ceiling.

How much paint for walls and ceiling of a 10x12 room?

With 8 ft ceilings: about 310 ft² of net wall plus 120 ft² of ceiling = 430 ft². Two coats at 375 ft²/gal with 10% waste ≈ 2.5 gallons.

Do ceilings need primer?

New drywall, water stains and smoke-damaged ceilings need a stain-blocking primer first. Previously painted, clean ceilings in the same colour usually do not.

Related calculators

How much paint do I need? →

Step-by-step guide with worked examples.

Concrete CalculatorVolume, bags or cement, sand and gravel for slabs, footings, columns and stairs.Tile CalculatorTiles, boxes, grout and adhesive for floors and walls in any pattern.Drywall CalculatorSheets, screws, joint compound and tape for walls and ceilings.Flooring CalculatorPacks of laminate, vinyl or hardwood plus underlay and baseboard.Quote MakerProfessional quotes for any trade with your logo, tax and a link your client can accept.