Embarking on a commercial painting project and wondering what the total cost is going to be? One of the first steps is determining how much paint you’ll need. And for that, you need to know the square footage of your space. But with high ceilings and intricate architectural details, this isn’t always straightforward.

Don’t you worry, this guide will walk you through the process, step by step.

builder worker painting facade of high-rise building with roller

Starting Simple: The Basics of Square Footage

At its core, calculating square footage is about multiplying the length of space by its width. Imagine your commercial space as a rectangle—even if it isn’t one. Measure the length and width, then multiply them together.

For example, a room that’s 20 metres long and 15 metres wide has a square footage of 300 square metres (20m x 15m = 300m²).

Factoring in Ceiling Height

If you’re painting walls, ceiling height matters. To calculate the square footage of a wall, measure its height and width, then multiply.

For a wall that’s 5 metres high and 15 metres wide, the square footage is 75 square metres (5m x 15m = 75m²). Remember to do this for all walls!

Professional decorators painting wall indoors. Home repair service

Navigating the Intricate

Arches, recesses, and mouldings can complicate things. For these, break them down into simpler shapes.

Imagine you have an arched window in your commercial space. This can be visualized as a combination of a rectangle (the bottom part) and a semi-circle (the arched top).

1. Calculate the Rectangle’s Area:

Measure the width and height of the rectangular part.
Formula: Area = Width x Height

2. Calculate the Semi-Circle’s Area:

Measure the width of the arch (which is also the diameter of the semi-circle).
Find the radius by dividing the diameter by 2.
Formula: Area of the full circle = π x Radius^2
Since we only want the area of the semi-circle (half the circle), divide the result by 2.

3. Combine the Areas:

Add the rectangle’s area to the semi-circle’s area to get the total square footage of the arched window.

For instance, if the rectangular part of the window is 1 metre wide and 2 metres high, its area is 2 square metres (1m x 2m). If the arch has a width (diameter) of 1 metre, its radius is 0.5 metres. The area of the semi-circle is approximately 0.785 square metres (π x 0.5^2 ÷ 2). Combining these, the total area of the arched window is approximately 2.785 square metres.

male workers painting building wall on the rope. Dangerous occupation concept.

Subtracting the Exceptions

You won’t be painting over doors and windows! Measure their square footage and subtract it from your total. For a standard door that’s 2 metres high and 0.8 metres wide, you’d subtract 1.6 square metres (2m x 0.8m = 1.6m²) from your total.

Tools to Make It Easier

While manual calculations have their charm, technology can simplify the process. Laser measures can quickly give you accurate measurements, and there are apps designed to calculate square footage with a few taps.


Calculating the square footage for commercial painting might seem daunting, but by breaking it down step by step, it becomes manageable. Always round up your estimations to ensure you have enough paint, and when in doubt, consult with a professional.