Paint Calculator

Estimate gallons or liters of paint needed per room based on wall dimensions, coats, and door or window deductions.

Room Dimensions

Room Length

Room Width

Room Height

Deductions

Number of Doors

Number of Windows

Paint Settings

Number of Coats

Coverage per Gallon

sq ft

Typical: 300-400 sq ft per gallon

Gallons Needed

2 gallons

Liters Needed

6.1 liters

Total Wall Area

352 sq ft

Door/Window Deduction

72 sq ft

Paintable Area

280 sq ft

Total Area (with coats)

560 sq ft

Approximate Cost

$70.00 @ $35/gal

Example

Input: Room 12 x 10 ft, 8 ft walls, 2 doors, 2 windows, 2 coats, 350 sq ft per gallon

Result: 2 gallons (6.1 liters); paintable area 280 sq ft

Walls 2 x (12 + 10) x 8 = 352 sq ft minus 72 sq ft for 2 doors (21 each) and 2 windows (15 each) = 280; 280 x 2 coats / 350 = 1.6, rounded up to 2 gallons.

Paint Needed by Room Size

Room (ft)	Paintable area	Gallons (exact)	Buy
10 x 10	269 sq ft	1.54	2 gallons
10 x 12	301 sq ft	1.72	2 gallons
12 x 12	333 sq ft	1.90	2 gallons
12 x 14	365 sq ft	2.09	3 gallons
14 x 16	429 sq ft	2.45	3 gallons
16 x 20	525 sq ft	3.00	3 gallons
20 x 24	653 sq ft	3.73	4 gallons

8 ft walls, 1 door, 2 windows, 2 coats, 350 sq ft per gallon. Walls only.

Enter the room dimensions in feet - length, width, and ceiling height.
Specify the number of doors and windows to deduct their area from the paintable surface.
Choose the number of coats you plan to apply and adjust the coverage rate if needed for textured surfaces.
Review the estimated gallons or liters of paint required along with the total paintable wall area.
Repeat for each room and add the gallon totals to estimate the paint needed for an entire house.

How Much Paint Do I Need for a Room?

To estimate paint, work out the wall area, take off doors and windows, multiply by the number of coats and divide by the coverage per gallon. A 12 x 10 ft room with 8 ft walls, 2 doors and 2 windows has 280 sq ft to paint. Two coats at 350 sq ft per gallon need 1.6 gallons, so buy 2.

Wall area is the distance around the room times the height: 2 x (12 + 10) x 8 = 352 sq ft. The tool then takes off 21 sq ft for each door and 15 sq ft for each window, the sizes of a typical 3 x 7 ft door and 3 x 5 ft window. It rounds up to whole gallons, and it also gives liters and a rough cost at $35 a gallon. The estimate covers walls only. Ceilings and trim need their own count.

Coverage is the number to adjust. Most paint cans list about 300 to 400 sq ft per gallon on smooth, primed walls. Rough textures, bare drywall and dark-to-light color changes soak up more. For those, lower the coverage to 250 or 300, or plan an extra coat. Two coats is the usual advice for an even finish. For a whole house, run the calculator for each room and add the totals. Keep leftover paint for touch-ups, and label it with the room and color. If you are papering a wall instead, use the Wallpaper Calculator.

Formula / How It Works

Wall Area = 2 x (Length + Width) x Height | Paintable Area = Wall Area - (Doors x 21 sq ft) - (Windows x 15 sq ft) | Gallons = (Paintable Area x Coats) / Coverage Rate, rounded up

Frequently Asked Questions

With 8 ft walls, one door and two windows, a 12 x 12 room has 333 sq ft of wall to paint. Two coats at 350 sq ft per gallon need 1.9 gallons, so buy 2 gallons. That leaves only a little spare, so a rough wall may need a third gallon.

Most interior paint covers about 300 to 400 sq ft per gallon per coat on smooth, primed walls. This tool uses 350 as a middle value. Check the label on your can and enter its figure. Textured walls and fresh drywall can drop coverage well below 300.

Usually, yes. One coat often looks patchy, especially over a different color or fresh patches. Two coats give an even color and a tougher finish. A paint-and-primer product over a similar color may cover in one, but plan for two when you buy.

The tool counts walls only. Work out the ceiling area as length x width, such as 12 x 10 = 120 sq ft. Divide by the coverage and multiply by the coats. At 350 sq ft per gallon, two coats on that ceiling need about 0.7 gallons, so one extra gallon.

Related Tools

Area Converter

Convert between square feet, square meters, acres, hectares, square kilometers, and square miles.

Unit Converters

Length Converter

Convert between meters, feet, inches, centimeters, kilometers, miles, yards, and nautical miles instantly.

Unit Converters

Concrete Calculator

Calculate cubic yards or meters of concrete needed for slabs, footings, and columns with optional waste factor.

Construction and Home

Wallpaper Calculator

Calculate the number of wallpaper rolls needed for a room with pattern repeat and door or window deductions.

Construction and Home

Tile Calculator

Calculate the number of tiles needed for any floor or wall area, accounting for grout gaps and waste percentage.

Construction and Home

Fence Calculator

Estimate the number of posts, rails, and pickets needed for a fence based on its length, post spacing, and picket size.

Construction and Home

Paint Calculator