How It Works

Simply enter the height, width, and length of each wall you plan to paint. The calculator will provide the total surface area and estimate the number of gallons of paint and primer required for your project. This tool takes into account standard coverage rates for both paint and primer. 

In this calculator, you can enter how many square feet one gallon of paint and primer can cover. This will help you determine the number of gallons of paint and primer needed for your wall project.

A gallon of paint can cover between 350–425 square feet, depending on the type of paint:

• Wall paint: 375–400 square feet
• Trim paint: 375–425 square feet
• Ceiling paint: 350–400 square feet
• Primer: 225–275 square feet 

How to calculate required paint for Walls and Ceiling?

To calculate how much drywall you need, you need to perform calculations in several steps. They are as follows with examples:

Step 1: Measure the Walls:

There are two pairs of walls:

Two walls with dimensions $$

$Area=\text{Height}\times \text{Length}$

$\text{Two wall area} =2\times (\text{Height}\times \text{Length})$$$
$$
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Two walls with dimensions

$Area=\text{Height}\times \text{Width}$

$\text{Two wall area} =2\times (\text{Height}\times \text{Width})$$$

$$$$

 $\text{Total Wall Area}=\mathrm{Two\; wall\; area}+\mathrm{Two\; wall\; area}$

Calculating the Ceiling Area:

The ceiling has the same dimensions as the floor:

$\text{Ceiling Area}=L\times W$
$$

Total Room Area Formula is:

$\text{Total Room Area}=\text{Total Wall Area}+\text{Ceiling Area}$

Step 2: Calculate number of gallons of paint required:

To calculate the number of gallons of paint required to cover a given area, you can use the following formula:

$\text{Gallons of paint required}=\frac{\text{Total area to be painted}}{\text{Coverage per gallon}}$

let's assume:

• Coverage per gallon = 350 square feet

Let's say you have an area of A square feet to paint. The calculation would be:

$\text{Gallons of paint required}=\frac{\text{A}}{\text{350}}$

Here's an example. If you need to paint a wall area of 1400 square feet:

$\text{Gallons of paint required}=\frac{\text{1400}}{\text{350}}$ = 4 

So, you would need 4 gallons of paint.

Frequently Asked Questions

How much does 1 gallon of paint cover?

A general rule of thumb is that 1 gallon of paint covers approximately 350 to 400 square feet of smooth, nonporous surface with one coat.

What is difference between paint and primer?

Paint provides color and a decorative finish to a surface, while primer prepares a surface for painting by creating a smooth, even base and promoting better adhesion for the paint. Primer can also block stains, seal porous surfaces, and provide additional benefits like mildew resistance.

How do I account for doors and windows?

The calculator allows you to enter the number of doors and windows. Their areas will be subtracted from the total wall area to provide a more accurate estimate.

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