HOME CALCULATOR
Paint Calculator
Estimate how much paint you need for your walls based on room dimensions, doors, windows, number of coats, and paint coverage.
The calculator estimates door and window openings using standard dimensions. Adjust the inputs if your project differs.
Paint coverage varies by product, surface, application method, and number of coats. This calculator provides an estimate only.
How Much Paint Do I Need?
The amount of paint you need depends on the total wall area, the size of doors and windows, the number of coats, and the coverage provided by the paint you are using.
This calculator estimates the paintable wall area and then determines the approximate amount of paint needed based on your selected coverage.
How to Calculate Paint Needed
Start by calculating the total wall area. For a rectangular wall, the area is calculated by multiplying the wall length by its height.
Wall area = length × height
If you are painting multiple walls with the same dimensions, multiply the area of one wall by the number of walls.
Subtract Doors and Windows
Doors and windows do not normally need to be painted, so their area can be subtracted from the total wall area.
This calculator uses standard estimated dimensions for doors and windows. If your openings are significantly different, the estimate may differ from the actual amount of paint required.
Account for Multiple Coats
If you plan to apply two coats of paint, the paint coverage required is approximately twice the paintable wall area.
For example, if your paintable area is 500 square feet and you apply two coats, the total coverage requirement is approximately:
500 × 2 = 1,000 square feet
Paint Coverage
Paint manufacturers normally provide an estimated coverage amount on the product label. Coverage can vary depending on the type of paint, surface texture, application method, and other conditions.
This calculator uses the coverage value you provide to estimate the number of gallons required.
Paint Calculator Example
Suppose you are painting four walls that are each 12 feet long and 8 feet high.
The total wall area is:
4 × 12 × 8 = 384 ft²
If two doors and two windows are deducted using the calculator's standard opening sizes, the paintable area is reduced accordingly.
With two coats and paint covering approximately 350 square feet per gallon, the calculator can then estimate the amount of paint needed.
Should I Buy Extra Paint?
It can be useful to have some additional paint available because actual coverage can vary. Rough or porous surfaces, darker colors, paint application technique, and additional coats can all affect how much paint is required.
For a specific project, always consider the coverage information provided by the paint manufacturer.
Related Home Calculations
You can also use our Area Calculator to calculate the area of individual shapes or our Square Footage Calculator for rooms and other rectangular spaces.
Frequently Asked Questions
How much paint do I need for a room?
The amount depends on the total wall area, doors and windows, number of coats, and the paint's coverage per gallon. Enter your measurements above to estimate the amount required.
How many square feet does one gallon of paint cover?
Coverage varies by product. Enter the coverage listed by your paint manufacturer into the calculator for a more useful estimate.
Should I subtract windows and doors?
Yes. Subtracting doors and windows can make the estimate more accurate because those areas generally do not need wall paint.
How many coats of paint should I use?
The appropriate number of coats depends on the paint, surface, color, and desired finish. Enter the number of coats you plan to apply.
Does paint coverage vary?
Yes. Actual coverage can vary based on the paint product, surface texture, application method, and other conditions.
Is the paint calculator exact?
No. The result is an estimate. Always check the manufacturer's coverage information and consider the characteristics of your specific project.