Paint Coverage Calculator
Estimate paint in US gallons from wall area, number of coats and the coverage stated on your paint can.
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How to Use the Paint Coverage Calculator
Measure the width and height of each wall in feet, multiply each pair, then add the areas. Subtract doors or windows you will not paint if you want a net wall area. Enter that area, the planned number of coats and the product’s coverage in square feet per US gallon. Select Calculate to see the volume and a whole-gallon purchase estimate.
Formula and Explanation
Gallons = Area × Coats ÷ Coverage
Multiplying area by coats gives the total surface coverage required. Dividing by coverage per gallon converts that requirement to paint volume. The whole-gallon suggestion rounds the calculated volume up; it does not add a separate allowance for waste.
Coverage varies with texture, porosity, application method and color changes. Primer is not calculated separately. Use the paint manufacturer’s coverage guidance for your surface and decide how much extra to keep for touch-ups.
Worked Example
For 400 square feet, two coats and a product rated at 350 square feet per gallon: 400 × 2 ÷ 350 = 2.2857 gallons. If buying only gallon cans, that means three cans before any extra allowance. Quart or smaller containers may change your shopping list.
Frequently Asked Questions
Should I subtract windows and doors?
Subtract openings that will not receive this paint to calculate a net area. Keep trim, ceilings and doors separate if they use a different product or coverage rate.
Where do I find the coverage per gallon?
Use the square-foot coverage on the product label or technical sheet. It is usually specified per coat and may be given as a range. Choose a value appropriate to the surface you are painting.
Does the result include primer and waste?
No. It calculates the entered area and coats at your coverage rate. Calculate primer separately and add your own allowance for spills, porous surfaces or future touch-ups.
Why does the purchase estimate round up?
Paint is commonly sold in fixed container sizes. A 2.2857-gallon requirement becomes three whole gallons when buying gallon cans only. You can choose a different combination of available sizes.
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