Paint calculator

Gallons = wall area less doors and windows × coats ÷ 400 sq ft a gallon: a 12 × 10 ft room with 8 ft walls, a door and two windows has 314 sq ft to paint, or 2 gallons for two coats.

Your measurements

Example

Use the unit shown for each box, or type another one: 12 ft 6 in, 150 in, 3.8 m and 600 mm all work, as do the marks on a tape measure.

Room 1

Length (ft) Width (ft) Wall height (ft) Doors Count them. The door size is in the details below. Windows Other openings you measured (sq ft) An archway, a patio door or any opening not counted above. Extra doors or trim surface (sq ft) Color and finish Name the paint, such as “Agreeable Gray, eggshell”. Rooms with the same name share their cans; each color gets its own count.

Measure from Surfaces Paint coats

Details Package sizes, prices and materials

Extra paint (%) Extra adds paint after the measured surface, coats and coverage are accounted for. Check those inputs first. Primer and trim use their own coverage and coat counts. No percentage here is a manufacturer recommendation. Door width A common door width from a door maker. Change it to your door. Door height 80 inches is the standard door height in rooms with 8-foot ceilings. Window width Window height 32 × 48 inches is one standard window size. Measure yours for a closer answer. Coverage per gallon (sq ft) Paint Benjamin Moore gives ben eggshell 400 to 450 sq ft a gallon. The store prices are for its eggshell gallon and, for the trim, its semi-gloss quart; choose another paint to leave them out. Can size (gal) Primer coats New drywall, patches and stains take primer, and so does a light color over a dark one, often tinted toward the new color. Set 0 to repaint a sound wall in a similar color: the paint label says when. Primer coverage per gallon (sq ft) Primer can size (gal) Your price per paint can ($) Trim to paint, total length Trim face height Measure the face of the baseboard or casing you will paint. Trim coats Trim paint container (gal) Doors to paint Both faces of each door, at the door size above, in the trim paint. Cabinet faces to paint (sq ft) Add up the doors and drawer fronts, both sides where you paint both, and the face frames.

Example: replace these measurements

Your material list

2 1-gallon paint cans+ 2 more items on the list

314 sq ft measured

Your measured layout

Room dimensions and a schematic door opening. Subtract measured openings. Include the ceiling only when you select it.

Your shopping list

2 1-gallon paint cans
1 1-gallon can of primer
1 quart of trim paint

At posted store prices

$109.98 2 × $54.99 a gallon, Benjamin Moore ben interior eggshell, 1 gallon at New York Paint & Hardware in New York, NY on Oct 19, 2026
$24.99 1 × $24.99 a quart, Benjamin Moore ben interior semi-gloss, 1 quart at New York Paint & Hardware in New York, NY on Oct 19, 2026

$134.97 for these 2 items, before tax and delivery.

Not priced here: 1-gallon cans of primer. Each price is one store’s posted price on the day shown, for the product named. Prices vary between stores: check yours. Your own price goes under Details.

Benjamin Moore’s data sheet says ben eggshell primes itself on most properly prepared surfaces, bare drywall and most wood included. It still calls for a primer on cured plaster, cedar, redwood and bare metal, a block filler on rough masonry, and a special-purpose primer on walls that are water-stained, smoke-damaged, greasy or very slick; some custom colors need a tinted primer too. If your walls are none of these, set Primer coats to 0 under Details.

Already have some? See what it covers

How many 1-gallon paint cans you have

Quantities and package details

Paintable area: 314 sq ft
Openings deducted: 1 door, 2 windows: 38 sq ft
Area across all coats: 628 sq ft
Paint before can rounding: 1.57 US gal
Paint volume before rounding: 5.94 liters
Surface 1: 314 sq ft
Primer cans: 1
Primer container: 1-gallon can
Baseboard length: 41.5 ft: the room perimeter less the doors
Trim area: 12.1 sq ft
Trim paint: 1 quart of trim paint

The calculation

Surface area: 314 sq ft
ceil(314 × 2 × (1 + 0/100) ÷ 400) = 2

Not measured yet? Common sizes

A rough starting point, worked out with this calculator. 8 ft walls, walls only, one door and two windows, two coats at 400 sq ft per gallon, no extra. Use a row to load its size into the calculator, then change it to your measurements.

Paint for common room sizes
Room	Wall area to paint	Paint before rounding	1-gallon cans
10 × 10 ft	282 sq ft	1.41 US gal	2
12 × 12 ft	346 sq ft	1.73 US gal	2
12 × 14 ft	378 sq ft	1.89 US gal	2
14 × 16 ft	442 sq ft	2.21 US gal	3
16 × 20 ft	538 sq ft	2.69 US gal	3

Common questions

How much paint do I need for a room?

Work out the wall area (the room’s perimeter times its height), subtract the doors and windows, multiply by the coats and divide by the coverage on the can. Sherwin-Williams calls its 400 square feet per gallon a theoretical figure: rough or porous walls take more.

Source: Sherwin-Williams paint questions. Listed on the Sources page.

How many coats of paint do I need?

The paint label and the surface decide. The calculator starts at two coats and counts primer separately, so you can change either.

Do I subtract doors and windows?

Yes. Count them and the calculator multiplies each by a size you can change: 30 by 80 inches for a door and 32 by 48 inches for a window.

Source: Marvin: Best interior door size for your home; Pella: Standard window sizes. Listed on the Sources page.

Should I buy quarts, gallons or a 5-gallon pail?

The size that leaves the least over. Switch the can size in the details to compare. Trim is usually a separate, smaller purchase: enter its length to count it.

How is the ceiling counted?

Choose walls and ceiling to add the room’s floor area as ceiling. Ceiling paint is often a different product: once you name the rooms’ colors, the ceilings get their own count.

How much paint do I need for rooms in different colors?

Count each color on its own and round each up to whole cans. Three rooms in two colors can need a can more than the same walls in one color, because each color has its own part-used can. Name each room’s color and finish and the list does this for you.

How much paint does a door take?

A 30 × 80 inch door is about 17 square feet a face, 33 for both. Two coats cover about 67 square feet, so a quart at 400 square feet a gallon paints one door with some left. Enter the doors under Details and they join the trim paint, with any cabinet faces.

How to plan the quantity

Wall area is the room perimeter times height. Count the doors and windows instead of measuring them: each count is multiplied by the door or window size in the details, which you can change. Add any other opening you measured in square feet. Add the ceiling only when you plan to paint it. Each room keeps its own openings.

Multiply the paintable area by the number of coats. Divide by the coverage on the can and round to the selected can size. Paint and primer have separate coat, coverage and can-size inputs.

A label’s coverage may not match a porous or textured wall. Adjust coverage for the product and surface instead of assuming every gallon does the same job.

Before you order

The baseboard, and any doors and cabinet faces you enter in the details, get their own trim list, usually a different finish in a smaller container. Repairs are a separate task. This does not choose a coating or decide whether primer is needed.
Name each room’s color and finish, and the list counts the cans color by color, with painted ceilings apart: rooms share cans only when they share a color.

Have prices moved?

Paint cost 5.0% more in September 2026 than a year earlier (Bureau of Labor Statistics producer price index, preliminary).

Every building material we track, month by month, with the change in a year.

Plan the work as well as the order: How to paint a room: prep, coats and cleanup.

Before ordering, read the guide: How much paint do I need? Coverage, coats and primer. Or choose another calculator.