Fast, free calculators and tools for everyday problems.
Estimate paint needed based on wall dimensions, coats, coverage rate, and openings.
A quick overview to help you understand what this tool does and how to use it well.
Use this paint calculator to estimate how much paint you need for a wall or room surface based on its size, the number of coats, and common openings such as doors and windows. This tool helps you avoid buying too little or too much paint when planning a painting project.
By adjusting the wall dimensions, number of coats, and paint coverage rate, you can get a quick estimate of the amount of paint required for both small touch-ups and larger home improvement projects.
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Your result updates after a successful calculation.
Estimated paintable area
110
Wall area after subtracting doors and windows in the selected unit system.
Gallons Needed
0.63
Approximate paint required based on coverage, coats, and the selected unit system.
Unit summary
Results shown in square feet and gallons.
Indicates whether the result uses imperial or metric paint wording.
See the formula, calculation method, and reasoning behind the result.
This calculator estimates paint needed by first calculating the total wall area, subtracting the area taken up by doors and windows, and then multiplying the remaining paintable surface by the number of coats.
The calculation takes into account:
In general, the process works like this:
This gives an estimated amount of paint needed for the project. Because real-world coverage can vary by paint type, surface texture, and application method, the result should be treated as a practical estimate rather than an exact guarantee.
Estimate paint for a 20 by 8 foot wall with one door, two windows, two coats, and typical imperial paint coverage. This example shows how the calculator accounts for wall size, openings, and multiple coats. Even a fairly large wall may require less paint than expected once doors and windows are excluded from the total paintable surface.
Example results
Common questions about this tool.
Yes. This version subtracts standard door and window area from the total paintable surface.
Extra coats increase the total paint required.
To estimate paint needed, calculate the total wall area, subtract any areas that will not be painted such as doors and windows, multiply by the number of coats, and divide by the paint coverage rate. This calculator does those steps for you automatically.
In many cases, no. Doors and windows reduce the paintable area, so excluding them can give you a more accurate estimate. This calculator accounts for them using simple default opening areas.
Each coat requires additional paint. If you plan to apply two coats instead of one, the total paint needed will increase because the paintable area is effectively covered twice.
Paint coverage rate is the amount of surface area one gallon or litre of paint can cover. The actual number depends on the product, surface texture, and application method, but manufacturers usually provide a recommended coverage estimate.
No, it is an estimate. Real paint usage can vary depending on surface texture, paint thickness, surface preparation, porosity, and whether you are using a brush, roller, or sprayer.
Yes, the calculator supports both imperial and metric workflows so you can estimate paint needs using the unit system that matches your project.