How much paint do I need to paint a wall?

Planning to update your room’s appearance, but no time for the whole renovation work? Painting the wall is the best alternative to consider.

Painting is one of the most popular DIY projects as this is the fastest way to transform a room’s appearance. Some are just hesitant because they have no idea how much paint will they need.

How much paint do I need to paint a wall?


In general, one gallon of paint can cover up to 400 square metre wall/room with a single coating. This may be a rough estimation, but it is still a great starting point. If the wall coverage isn’t as big as that, you can determine the amount of paint to use either of the following methods.

Manual calculation

Related Article: Painting Services Cost Guide

The answer to the question, ‘how much paint do I need to paint a wall?’ is not as difficult as everyone thinks of. You just need to consider a number of factors to ensure that you get the exact amount of paint to use.

1. Measure the wall

Start the project by identifying the number of walls you want to paint. For each wall, measure the height and width then multiply it to one another. After getting the total surface of each wall, add all the figures.

After getting the total surface of the wall, you can then measure all the breaks in the wall (e.g. fireplace, windows, etc). Deduct the total of each from the wall’s total surface of the wall. The result is the surface area (i.e. square metre) that you need to paint.

Lastly, divide the total surface of the wall by the coverage rate. The coverage rate is typically found on the paint’s label. After computing it, you can immediately buy the paint you prefer.

2. Determine the condition of the wall

Older walls tend to consume more paint compared to a new wall. For new walls, you just need a high-quality paint. This may cost a little bit higher, but it can still save you money on primer (since you won’t be needing it).

For older walls, it requires not only more paint but also with the work required for the preparation (particularly if the wall shows signs of rust). It’s smart to let a professional painter to do the job or even just seek for advice. They will guide you about the best painting techniques to use to make the process easier and complete the task faster.

3. The number of coats needed

No one can ever fully identify the amount of paint that you need without considering the number of coating required per wall. You can determine the number of coatings by checking the AS/NZS 2311 and material used.

AS/NZS 2311 is an Australian Standard that covers the proper painting system to apply per substrate. This also includes proper techniques to use in the paint application: spray painting, brush, or rollers.

Materials used in walls are important to consider too because they have different abilities or reaction in absorbing paint. There are some that absorb paint well, but some require more coating before reaching your desired result. It’s ideal to consult a professional painter for you to fully understand the needs of your wall.

You might also want to read: Interior Painting 101: Tips from Local Painters

Using paint calculator

Since not everyone is a fan of math, some painters just decide to create their own paint calculator to make it simpler for their customer.

The customer just needs to fill up the box with the right measurements (walls, doors and windows), the number of windows, doors and coating; and lastly, the description of the job – is it for a repaint or new painting job?

Upon clicking the ‘calculate’ button, it will show the total number of gallons or litres of paint to use. You can see the paint calculator on the painter’s business website.

Whichever of the two you opt to choose in determining the exact amount of paint to use, always remember to align it with the Australian Standard regulations (AS/NZS 2310, 2311 and 2312). This regulation covers the proper painting system to apply per substrate and other information that help to protect the wall.

Featured Photo Courtesy of Free-Photos via Pixabay

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