How Much Paint Do I Need for a Room? Gallons by Room Size

September 28, 2026

A 12 by 12 foot room with 8 foot ceilings needs about 2 gallons of paint for two coats on the walls, plus 1 gallon for the ceiling. For any room, measure the wall area, subtract doors and windows, double it for two coats, and divide by 350. That's how much paint you need, in gallons. Two gallons of PRO on the walls and 1 gallon of EKO on the ceiling come to $155. Local delivery in New York and New Jersey is free over $150.

How many gallons of paint for a room

Two coats on smooth walls, 8 foot ceilings, one door and two windows:

10 by 10 foot room: 270 square feet of wall, 2 gallons.
12 by 12 foot bedroom: 334 square feet, 2 gallons.
12 by 14 foot bedroom: 366 square feet, 3 gallons.
14 by 16 foot living room: 430 square feet, 3 gallons.
Ceiling of a 12 by 12 room: 144 square feet, 1 gallon.

Rough walls or a big color change may need an extra coat. Size it by area: multiply the wall area by three instead of two, divide by 350 and round up. Prewar ceilings change the count too. A 12 by 12 room with 10 foot ceilings has 430 square feet of wall and takes 3 gallons.

How much paint do I need: the math

Add up the length of every wall in feet. That's the perimeter.
Multiply by the ceiling height.
Subtract about 20 square feet for each door and 15 for each window.
Multiply by two for two coats.
Divide by 350 and round up to the next whole gallon. A gallon covers 300 to 400 square feet per coat, and 350 is the middle.

Worked example: a 12 by 14 foot bedroom with 8 foot ceilings, one door and two windows. 52 feet of wall times 8 is 416 square feet. Take off 50 for the door and windows and you're at 366. Two coats is 732. Divide by 350 and you get 2.1. Two gallons leave you short, so buy 3, or a 5 gallon pail if more rooms are coming. The paint calculator on our home page uses 300 square feet per gallon and counts doors and windows in, so it leaves you a margin. Use 350 to price the job and the calculator to make sure you don't run short.

Ceilings and doors

Ceiling: length times width, times two coats, divided by 350. A door is about 20 square feet a side. Both sides with two coats come to 80 square feet, so one gallon paints about four doors.

Brick, stucco and new drywall

Brick, stucco and raw concrete soak up more paint. Figure them at 300 square feet a gallon or less.

Let joint compound dry completely and new plaster cure for at least 30 days before any of it. Then bare drywall and plaster start one of two ways. One coat of PRIME, then two coats of EKO or NEO. Or at least two coats of PRO, a paint and primer in one, with no primer. For PRIME, run the math with one coat: the walls of a 12 by 12 room take about 1 gallon. PRIME comes only in a $179 pail that primes 1,500 to 2,000 square feet. For a single room, PRO with no primer is the simpler buy. Full steps are in our guide to primer for new drywall.

How much to buy: gallons or a 5 gallon pail

Pick the line first. Walls, trim and doors take PRO, a 100% acrylic paint and primer in four sheens. NEO is a flat or satin acrylic for walls and ceilings, inside or out. EKO is a zero VOC interior flat for walls and ceilings, made for rentals and turnovers.

PRO costs $58 a gallon or $285 for 5 gallons, which is $57 a gallon. NEO is $49 a gallon or $218 for 5, about $44 a gallon. EKO is $39 a gallon or $165 for 5, which is $33 a gallon.

At 5 gallons the pail always wins: $218 instead of $245 on NEO, $165 instead of $195 on EKO, $5 less on PRO. At 4 gallons, look at the pail anyway. Four gallons of EKO cost $156, and the pail costs $9 more for a fifth gallon.

Price and delivery

Local delivery in New York and New Jersey is $15 per order, free over $150. Every 5 gallon pail qualifies for free local delivery in New York and New Jersey, and so does the $155 bedroom order above. Orders ride on our own truck. Delivery runs on business days, to the curb or the ground floor entrance. Factory colors in stock usually go out the same day. Custom tinted orders placed before 2pm on a business day are normally mixed that day. From November to March we check the forecast along the route, and if it drops to 32°F anywhere on the way, we hold your order and call you first. Details on our delivery page.

Open the paint calculator

Questions we get

How much paint per square foot?

One gallon covers 300 to 400 square feet per coat. Plan on a gallon for every 350 square feet of each coat.

Do I need two coats?

Yes. Kompozit's data sheets call for at least two coats on new and uncoated surfaces.

How do I keep the color even across several cans?

Mix cans of the same product, sheen and color together in one bucket before you start. The data sheets ask for this whenever a job uses more than one container.