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This paint calculator estimates wall gallons for a rectangular room. Enter the openings you will not paint, the number of coats, and the square feet per gallon from the can. Coverage labels vary.
Paint to buy
2.40gal
Planning estimate from the numbers you enter. Coverage, density, waste and price are assumptions, not a supplier quote or an engineering specification.
How it works
Gross wall area is the perimeter times the height: 2 × (length + width) × height. Subtract doors and windows. Multiply by coats, divide by the coverage per gallon, and add a waste percent for color changes, texture, and the bottom of the can. The default coverage is 350 square feet per gallon per coat, a common label range, not a promise. Porous drywall and a deep color often cover less. Ceilings and trim are separate areas. Add them as their own run or include them in the openings math only if you mean to.
Formula
Gallons = net area × coats ÷ square feet per gallon × (1 + waste ÷ 100). The result also rounds up to a whole gallon so you can see the can count. Cost uses your price per gallon times the unrounded gallons.
Example
The gross walls are 432 square feet. Net is 382. Two coats at 350 square feet per gallon, plus 10% waste, is 2.40 gallons. Buy 3 gallons. At $45 per gallon the paint is about $108.05 before tax.
Tips
Labels often quote a range and assume a smooth, primed surface. A first coat on new drywall is not the same as a same-color repaint. Primer is another product. Do not assume one gallon of paint primes and finishes.
Equipment
Lifts and commercial spraying equipment can fall in Dengaro's $15,000 to $2 million equipment range. The calculator button opens an equipment application. It does not order paint.
Important questions
No. The formula is the four walls. A ceiling is length times width, divided by coverage, with its own coats. You can run that area through the square footage calculator and divide.
The square feet you will not paint. A standard door is often estimated near 20 square feet and a window near 15, but measure if the units are large. The default 50 is an example, not your room.
Cans do not divide evenly, and texture, color, and touch-up use more than the ideal coverage. Ten percent is a starting assumption. Set it to 0 if you want the bare formula.
No. Replace it with the figure on the product. The calculator will not override a number you type.
Financing built into the sale