Mai Pham
January 10, 2023

At my home, since we bought a robot vacuum, we literally only clean the house ourselves once a year. We completely rely on our robot vacuum for the rest of the year. After such a long time letting the robot vacuum do its job, we can really see the good and the bad of our robot vacuum. When it’s time to invest in a newer one, I have to research how robot vacuums’ shapes impact their cleaning ability and why many robot vacuums are round.

Most robot vacuums are round because roundness improves autonomy. According to Joseph Lee Jones, one of Roomba’s investors, when a round robot vacuum wanders into a corner or narrow space it can always use the strategy of turning in place until it finds a way out. This strategy requires no sensor other than a bumper. A non-round robot must execute a more complex series of maneuvers to extricate itself. Also, the correct moves can’t be computed unless the robot knows the shape of the local space. Thus a non-round robot is more likely to get stuck.

Let’s go into a little bit more detail on robot vacuum shapes and compare how these shapes can impact its cleaning.


The most traditional and cheapest navigation system is the bump-and-run. It means your robot vacuum will run until it bumps into something, and then it will change direction accordingly.

Other more advanced navigation systems are Lidar, Smart Laser, Dual Eye, etc. just to name a few. These advanced systems will help a robot vacuum to detect its location, and the area it is in as well as decide how to maneuver in that area.

In general, round shape robot vacuums can feature from the cheapest to the most advanced navigation system while the D-shape and square shape robot vacuums must feature an advanced navigation system to avoid getting stuck. However, even with the most advanced navigation system, a D-shape and square shape robot vacuum can still get stuck in narrow places.

How Close It Gets To Corners

The biggest advantage of D-shaped and square compared with round robot vacuums is that they can get closer to the corners and wall edges.

When it comes to cleaning corners, with time, round robot vacuums prove their ineffectiveness. No matter how long their side brushes are, round robot vacuums can not get to the last speck of dust. Through time, those tiny speck of dust is all stored in your corners.

Do Robot Vacuums Clean Corners
A corner with only round robot vacuum cleans

Unlike round robot vacuums, D-shape and square shape allow these robot vacuums to get closer to the wall edges and corners to clean better.

What’s more, with the flat edge, D-shaped and square robot vacuums are able to position the main brush at the front of the robot while the round robot vacuums often have the main brush at the center. Thanks to this position, D-shaped and square robot vacuums are better at the cleaning ability at corners and along edges.

How D-shape robot vacuums get closer to corners

Brush Size

Brush sizes greatly impact on how well a robot vacuum cleans, how fast it can complete a cleaning session and how much time you have until its battery runs out.

For round robot vacuums, the brush size length is limited as it has to make room for the wheels. But with D shape and square shape, the brush size length can be much longer as it can be located at the front without blocking the wheels. The famous D-shape robot vacuum Neato has a main brush that is nearly double the size of those on regular round robot vacuums.

With long brush, a robot vacuum can complete a cleaning session in less rounds and can clean up to a larger area before the battery runs out.


Round robot vacuums can reduce the bumping and impact on other furniture, even with the bump-and-run navigation. With a very light bump, they can recognize the obstacles and make decisions to go around or change direction. Because of the round shape, the scratches to your furniture is minimum.

Square robot vacuums have contoured corners. Therefore, they will likely to leave less bumps and scratches.

Compared with round robot vacuums, D shape robots still have 2 quite pointy corners, so they can leave marks and bumps on your furniture. But again, D shape robot vacuums only feature a more advanced navigation system to avoid bumping into obstacles.

Robot Vacuum Shapes Greatly Impact The Cleaning Ability

When ensuring you get the best out of its main function: vacuum, it is important to know your expectation toward your robot vacuums. What is your house layout? Does it have a lot of corners? Does it have narrow places? Do you have valuable furniture?

As can be seen, there are 3 most common robot vacuum shapes and they all can have a say in how well your robot vacuum can do its job. So make sure you look through these factors to decide which one suits you the most.

If you still have tons of questions on robot vacuums, check out my guide on robot vacuum types, prices and features.

About the Author

I am a working mother who more than often prefer to come home and rest rather than doing house chores. I am passionate about simplifying house chores to live and enjoy life more.

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