How Many Gallons of Paint Per Square Foot? A Coverage Guide

One gallon of paint covers about 350 to 400 square feet with a single coat on a smooth, primed surface. In gallons per square foot, that is about 0.0025 to 0.0029 for one coat, or roughly a quart for every 100 square feet. Plan on double that for two coats.

That is also the answer to how many square feet 1 gallon of paint covers, and a second coat cuts the figure to about 175 to 200 square feet per gallon. Primer covers less, usually 200 to 300 square feet per gallon, because it soaks into bare surfaces. The number on the can is a starting point, not a guarantee, since your walls decide the real coverage.

The same four steps work for a bedroom or a full exterior. Here they are using a 12 by 12 foot room with 8 foot ceilings, one door, and one window.

The answer stays at 2 gallons whether your paint covers 350 or 400 square feet per gallon, which tells you the estimate holds up. If your result lands just over a whole number, buy the next size up or add a quart. This is the same formula a paint coverage calculator runs behind the scenes, so you can check any online tool against your own numbers.

Already know your paintable area? This chart uses 375 square feet per gallon, the middle of the 350 to 400 range.

Round up to the next full gallon, and check the result against your own measurements before you buy.

Label coverage assumes a smooth, previously painted wall. Real walls rarely cooperate, so adjust your total with the factors below.

The high end of the texture range applies to very rough surfaces. PaintCare, a nonprofit paint stewardship group, notes that rough textures can take up to about 50% more paint and glossy sheens cover less than flat.

If the home predates 1978 and the paint is failing or unknown, the EPA's guidance on lead-safe renovation covers what to check before prep work. Many older Twin Cities homes fall into this group, and our guide to testing for lead in paint in Minnesota walks through the next steps.

Exteriors follow the same formula with a few extra steps. Multiply the distance around the house by the wall height, subtract windows and doors, and add each gable (width times height, divided by two). Exterior paint spreads a little thinner than interior paint, so use about 250 to 350 square feet per gallon instead of 375.

Take a one-story house measuring 40 by 30 feet with 10 foot walls, 12 windows, 2 doors, and two gables that are 30 feet wide and 8 feet tall. The walls come to 1,400 square feet. Windows and doors take off 220, and the two gables add 240, for 1,420 square feet. Two coats means 2,840 square feet of coverage, and at 300 square feet per gallon that is about 9.5 gallons, so buy 10. Trim and gutters add roughly 1 gallon for every 8 gallons of body paint, so budget one or two more.

Stucco changes the answer fastest. Weathered wood and rough stucco, both common on older Minneapolis and St. Paul homes, soak up more paint than smooth siding. The same house on rough stucco at 250 square feet per gallon needs about 11.4 gallons, so plan on 12. If you are weighing a repaint on stucco, our guide to the signs of stucco problems covers what to fix first, and the notes on painting older homes in the Twin Cities explain why prep matters so much on them.

These are illustrations, not quotes. Measuring your own house, or having a crew do it as part of an exterior house painting estimate, gives the real number.

Walls are only part of the shopping list. Ceilings are length times width, run through the same four steps. In the 12 by 12 room, the ceiling adds 144 square feet per coat. Painted with the same paint, two coats on the ceiling add about 0.8 gallon to the 1.86 for the walls, a total of about 2.6, so buy 3 gallons. The steps in our guide on how to paint a ceiling cover the technique.

Primer covers about 200 to 300 square feet per gallon and belongs on bare wood, repaired drywall, stains, and big color changes. Skipping it usually costs more paint later, since the finish coats soak into the bare surface. Give each coat the time it needs, as the guide on how long to wait between coats of latex paint explains.

Trim takes less than most people expect. About 48 feet of 4 inch baseboard is roughly 16 square feet per coat, and a quart covers about 90 to 100 square feet, so one quart handles the trim in a room this size.

A single bedroom is a fine do-it-yourself estimate. Full interiors, houses with several siding types, and jobs with heavy prep are harder to size from a tape measure, because repairs, color changes, and surface condition all change the total. That is where a walkthrough beats a formula. A crew measures every surface, spots the ones that will drink extra paint, and puts the number in writing, and both interior house painting and exterior estimates start that way.

Round up, always. Buying one gallon short means a second trip, and with a tinted color the new can may look slightly different from the first. A good habit is to buy enough for a whole wall in one purchase and keep a quart for touch-ups.

Extra paint costs money, so it helps to know what a gallon runs before you stock up. Our guide to what a gallon of paint costs breaks the price down, and the interior painting cost guide and exterior painting cost guide show how paint fits into a full project. Interior rooms typically run $500 to $600 each, and a standard Twin Cities exterior runs about $6,000 to $8,000.

Durahome estimates on the high side over the phone and often comes in lower, and the written estimate is exact and always free. It also breaks out ceilings, trim, and add-ons as their own lines instead of burying them in one total.

Durahome is a Painting Contractors Association member and fully licensed and insured, with a 4.8 Google rating from 140 reviews. Every estimate carries the same trust stack, whether the job is one room or a full exterior.