Why Are Manhole Covers Round? The Surprising Reason Explained

Manhole covers are a common sight on city streets and sidewalks, but have you ever wondered why they are round?

In this article, we will explore the surprising reason why manhole covers are round and delve into the history behind this common urban feature.

The Practical Reason

Stability and Safety The primary reason why manhole covers are round is for stability and safety. A round cover cannot fall through its opening, unlike a square or rectangular cover that could become trapped diagonally. Additionally, a round cover can be easily rolled to move it out of the way, which is important for emergency responders and maintenance crews.

The Historical Reason

Manufacturing and Design While the practical reason for round manhole covers is the most important, there is also a historical reason for their shape. Early manhole covers were made of cast iron, which was easier to shape into a round form than a square or rectangle. Additionally, a round cover required less material than a square or rectangle cover, making it more cost-effective to manufacture.

The Technical Reason

Load Distribution Another technical reason for the round shape of manhole covers is load distribution. A circle distributes weight evenly in all directions, making it the ideal shape for a cover that will be supporting heavy loads. A square or rectangle cover would be more likely to crack or break under the weight of heavy vehicles.

Interesting Facts About Manhole Covers

  1. The earliest manhole covers can be traced back to the Roman Empire.
  2. Manhole covers are round for a reason. A round cover can’t fall down a round hole, but a square cover can.
  3. Manhole covers can weigh hundreds of pounds. This is why it’s vital for them to be adequately secured—so they don’t cause severe damage or injury.
  4. Manhole covers are made of a variety of materials, including cast iron, concrete, and steel.
  5. Manhole covers are often decorated with symbols or images that represent the city or town they’re in.
  6. Manhole covers can be found all over the world, from the streets of New York City to the streets of London.
  7. Manhole covers are an important part of our infrastructure, and they help to keep our cities running smoothly.
  8. Manhole covers are often recycled and reused, which helps to reduce waste.
  9. Manhole covers can be a source of art and creativity, and some people even collect them.
  10. Manhole covers are a fascinating part of our everyday lives, and they’re often overlooked.


In conclusion, manhole covers are round for practical, historical, and technical reasons. The round shape provides stability and safety, is easier and more cost-effective to manufacture, and distributes weight evenly.