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A Brushstroke of Knowledge: Calculating Paint for Your Interior Painting Project

Are you gearing up for a transformative interior painting project? Whether you're refreshing your living room, revamping your kitchen, or adding a splash of colour to your bedroom, one crucial step in the process is determining how much paint you'll need. After all, running out midway through the project can be quite the hassle. Fear not, for in this guide, we'll walk you through the process of calculating the right amount of paint for your interior project.

Step 1: Measure Your Walls

Before diving into gallons and litres, grab a tape measure and calculate the square meterage (m2) of the surfaces you plan to paint. Measure the length and height of each wall you intend to cover. For accuracy, measure the width of each wall and multiply it by the height to find the total square meterage. Don't forget to subtract the area of any doors and windows from your total.

Step 2: Determine Paint Coverage

Different paints offer varying coverage capacities. For standard emulsion paint, which is commonly used for interior walls in the UK, you can expect coverage of around 12 square meters per litre for the first coat on a smooth surface. However, this can vary depending on factors such as the porosity of the surface and the colour of the paint.

Step 3: Do the Math

Once you have your square footage and know the coverage per litre, divide the total square meterage by the coverage per litre to get the number of litres needed for one coat.​

For example, if your total square footage is 400m2 and the coverage per litre is 12m2:

Litres Needed = 400 Divided by 12 = 33.33

Litres of paint needed ​= 33.33

Step 4: Account for Additional Coats

Most painting projects require more than one coat for optimal coverage, especially if you're transitioning between significantly different colours or covering imperfections. Multiply the calculated litres needed for one coat by the number of coats you plan to apply. This will give you the total litres needed for the project.

Step 5: Round Up

It's always better to have a bit more paint than you need than to run out midway through your project. Round your final calculation up to the nearest whole number or, if purchasing paint by the gallon, consider buying an extra gallon (5 litres) to ensure you have enough to finish the job without interruption.

Step 6: Consider Prime and Trim

Don't forget to account for primer and any trim or accent colours you plan to use. These will require additional paint beyond what you've calculated for the walls.

Online Paint Calculator: To make things easier, there is an online paint calculator which does all the math for you.

You can find it here:


With these simple steps, you can confidently determine how much paint you'll need for your interior painting project. By accurately estimating your paint requirements, you can avoid the frustration of running out mid-project and ensure a smooth and successful painting experience. So grab your paintbrushes, roll up your sleeves, and let your creativity flow as you transform your living space with a fresh coat of color. Happy painting!

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