Free paint cost calculator. Enter wall area, coats and paint price to find how many gallons you need, primer gallons, and your total room painting cost.
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Enter your values and press Calculate.
This paint cost calculator starts with your paintable wall area: total wall area minus about 21 square feet for each door or window. It multiplies by your number of coats, divides by the coverage rate (350 to 400 sq ft per gallon for most interior paint), and adds your waste allowance for touch-ups. You always buy whole gallons, so the exact figure is rounded up. Example: a 400 sq ft room with 2 openings, 2 coats, 350 sq ft coverage and 10 percent waste needs 358 × 2 / 350 × 1.1 = 2.25 gallons, so you buy 3 gallons. Primer is one coat over the paintable area, costed at about 65 percent of the paint price per gallon.
The core formula is: gallons = (wall area - openings × 21) × coats / coverage × (1 + waste). Each input has a job. Wall area is the raw square footage of every wall you will paint. Openings subtract about 21 sq ft each, the average door or window you do not paint. Coats multiply the area because a second coat covers the same walls again. Coverage divides it: a gallon rated at 350 sq ft per gallon stretches further than one rated at 300. Waste adds your safety margin. Because paint is sold in whole gallons, the final number rounds up, which is why the exact gallons and the gallons to buy are shown separately.
A 12x12 room with 8-foot ceilings has four walls of 12x8 = 96 sq ft each, 384 sq ft total. Subtract 2 openings (42 sq ft) to get 342 sq ft of paintable area. Two coats doubles that to 684. At 350 sq ft per gallon that is 1.95 gallons; with 10 percent waste, 2.15 gallons, so you buy 3 gallons. At $45 a gallon the paint costs $135, plus one primer coat: ceil(342/350) = 1 gallon of primer at about $29, for a $164 total. This is the single most searched paint question, and the table-free math above is exactly what the tool runs.
Not all gallons cover the same area. Flat and matte interior paints cover the most, roughly 350 to 400 sq ft per gallon, because they have no sheen-building resins. Eggshell and satin, the most popular wall finishes, cover about 300 to 350 sq ft per gallon. Semi-gloss and gloss, used on trim and in bathrooms, cover the least, about 250 to 300 sq ft per gallon, and usually need an extra coat for full hide. Exterior paints vary more with surface texture: smooth siding near 350, rough stucco as low as 200. If your paint's label states a coverage rate, enter it in the tool; the default 350 matches the most common interior flat.
Yes, subtract doors and windows from the wall area, and this calculator does it automatically at 21 sq ft per opening. A standard interior door is about 21 sq ft and a typical window 12 to 15, so 21 per opening is a fair blended average. Large openings like sliding patio doors deserve a manual adjustment: measure them and reduce your wall area entry. Ceilings are a separate job: ceiling paint is usually flat white with its own coverage rate, and one gallon covers a 12x12 ceiling in a single coat. For walls and ceiling together, run the tool once for walls and once for the ceiling area.
Two coats is the professional standard for walls: the first coat seals and covers, the second evens out color and sheen. One coat works only for touch-ups or repainting the same color in good condition. Primer is the coat before the coats: it is required on new drywall, bare wood, patched areas, and dramatic color changes (dark to light especially), and it prevents the topcoat from soaking in unevenly. Primer covers like paint, about 350 sq ft per gallon, and costs roughly 65 percent of topcoat price, which is the ratio the calculator uses. Skip primer and you often pay for it in a third topcoat instead.
Five-gallon buckets typically save 5 to 10 percent per gallon versus single gallons, which matters on multi-room jobs. Three gallons at $45 is $135; a 5-gallon bucket at $205 would cover the same 3 gallons of need with 2 gallons spare for $70 less per gallon of actual need, but only if you will use the extra paint. The wasteful move is buying a 5-gallon bucket for a one-room job and storing 3 gallons you never touch. Rule of thumb: if your buy figure is 4 gallons or more, price a 5-gallon bucket; under 3 gallons, stick with single gallons.
DIY paint cost is materials only: paint, primer, plus $50 to $100 in supplies (rollers, tape, drop cloths). Professional painters typically charge $2 to $6 per square foot of wall area, or $300 to $800 per average room including materials, so a 400 sq ft room that costs you $160 in paint might cost $600 to $900 hired out. The trade is time: a pro crew paints a room in a day; a first-timer needs a weekend plus prep. This calculator prices the DIY route. If you are comparing quotes, divide each quote by your wall area to get the per-square-foot rate and compare apples to apples.
Step 1: pick your currency so every cost line reads in your money. Step 2: enter total wall area in square feet (measure each wall's width times height and add them). Step 3: enter the number of doors and windows. Step 4: choose coats (2 is standard) and your paint's coverage per gallon from its label (350 is typical). Step 5: enter the price per gallon, whether you need primer, and your waste allowance (10 percent is normal). Press Calculate to get exact gallons, whole gallons to buy, paint and primer cost lines, and the total.
Most interior paints cover 350 to 400 sq ft per gallon in one coat. Eggshell and satin cover 300 to 350, semi-gloss 250 to 300. Check your paint's label and enter its exact rate in the calculator.
Yes. This calculator subtracts about 21 sq ft per door or window automatically. For very large openings like patio doors, measure them and reduce your wall area entry by hand.
Two coats is the standard for interior walls: the first covers, the second evens out color and sheen. One coat only works for touch-ups or repainting the same color over paint in good condition.
Buy 10 percent extra beyond the exact gallons for waste and future touch-ups, and always round up to whole gallons since paint is sold that way. Keep the leftover can labeled with the room and color.
Yes for new drywall, bare wood, patched spots, stains, and big color changes. No for repainting the same color over sound paint. Primer costs about 65 percent of topcoat price per gallon, which is what this calculator assumes.
One coat over the paintable wall area: primer gallons = paintable area / coverage, rounded up. A 342 sq ft room at 350 coverage needs 1 gallon of primer.
Typically $2 to $6 per square foot of wall area, or $300 to $800 per average room including materials. Divide any quote by your wall area to compare painters fairly.
Budget paint runs $25 to $35 per gallon, mid-range $35 to $55, and premium $60 to $90 or more. Five-gallon buckets usually save 5 to 10 percent per gallon on bigger jobs.
Roughly yes, but ceiling paint is usually flat white and ceilings need only one coat. Run the calculator separately with your ceiling area and 1 coat for the ceiling figure.
Yes: add up the wall area of all rooms, count all openings, and run the calculator once. It is more accurate than per-room rounding because the rounding up happens once at the end.
A professional crew does an average room in a day. A DIY first-timer should plan a full weekend: a day for prep (tape, patch, sand) and a day for two coats with drying time between.