How to Calculate the Amount of Render Needed for a Project?

Render is a thin layer of plaster, cement, or other material applied to walls and ceilings. It protects the surface underneath it from weathering, spills, and wear and tear.

If you’re planning on applying render to a wall or ceiling in your home or outside space, you need to know how much render you will require so that you can purchase the right amount for your project. This article provides an overview of how to calculate the amount of render needed for a project.

contractor plaster rendering a brick wall

Types of Render

Before calculating the amount of render required for a project, it’s important to understand the different types available. The type of render used depends largely on the specific application – some are designed for interior surfaces, while others are better suited for outdoor walls and surfaces. Common types of render include:

Acrylic Render

Popular for both interior and exterior applications, acrylic render is a water-borne product with good flexibility which makes it resistant to cracking caused by weathering or temperature changes.


Polymer-Modified Render

This type of render contains polymers which increase its adhesive properties. It’s highly flexible and waterproof, making it suitable for use in damp environments such as bathrooms or basements.


Silicone Render

Silicone render is highly breathable and moisture-resistant, making it ideal for exterior walls exposed to extreme weather conditions.


Calculating the Amount of Render Needed

Once the type of render has been chosen, it’s time to calculate the amount required. The first step is to measure the area that needs to be covered. To do this, use a measuring tape and measure from one corner to the next across the wall or ceiling. Multiply the length and width together to get the total area (in square metres).

Now you need to factor in how thick you want your layer of render to be – typically 3-4mm for interior walls and 4-5mm for exterior walls. Divide this thickness by 10 so that you can convert millimetres into centimetres.

Now take your area measurement (square metres) and multiply it by 0.1 (the thickness in centimetres). This is the total amount of render you need, in cubic metres.

For example: A wall measuring 5m (length) x 2m (width) requires a layer of render 4mm thick. The area measurement is 10 square metres, so 0.4 metres cubed is the amount of render required (10 x 0.1 = 1; 1 x 0.4 = 0.4).


Other Considerations

When calculating the amount of render needed for a project, there are some other things that should be taken into consideration as well:

  • If the substrate surface has been painted previously, it may require special primers and sealants to ensure proper adhesion.
  • If textured walls are being rendered, they will require more render than a smooth wall.
  • The surface underneath the render should be flat and even – any imperfections may need to be corrected prior to applying the render.
  • Depending on the type of render used, an undercoat or bonding agent may also be necessary before applying the finish coat.



Calculating how much render is needed for a project can seem like a daunting task, but it’s actually quite simple once you understand the process. By following these steps, you’ll be able to determine exactly how much render you need for your project – ensuring that you purchase the right amount and get the best possible results.


Also Read

Comparing the Durability and Longevity of Applied Renders