Why Do Boats Have Round Windows (Portholes)?

why do boats have round windows

Have you ever stopped to ponder, why do boats have round windows? Although this question may not be the most common aspect of boats that is asked about a lot, the information we have prepared for you regarding round windows and portholes will surely be an enriching experience, especially for those with an inquisitive or engineering-based mindset.

If you would like to learn about the history behind portholes, the significance and benefits of round window designs, and why it is important to have portholes on your personal boat, then keep reading!

The History Behind Portholes

Interestingly enough, the history behind portholes has nothing to do with the port side (left side) of the ship, nor was it originally intended for viewing through it.

Portholes actually originated way back in 1485 during the reign of King Henry VII in England. To arm his naval fleet, King Henry VII insisted on equipping his ships with large-caliber weaponry that would be incapable of being mounted traditionally (via the forecastle and aftcastle).

This brought about the brilliant innovation of French shipbuilder James Baker, who suggested piercing the sides of the ships so that the cannons could be mounted inside the forecastle and aftcastle, rather than on it.

When the cannons were not in use, these portholes were covered with glass panels, which we would now technically refer to as the port lights (thick covers made of glass that serve as both opening and protection for the porthole).

Why do Boats Still Have Portholes?

Today, we still see portholes and port lights used often in every type of ship and boat, no longer for weaponry such as cannons and the like, but for more practical and convenient reasons.

First, having a porthole would allow for the entry of light into certain areas of the ship that require a high degree of visibility. Certain rooms and areas of a boat are not illuminated by artificial light at all times, mainly because of the expenses and waste of fuel energy which the boat will eventually run out of (this is critical during long voyages or cruise travels).

Second, some portholes have still retained the feature of being opened to allow for the entry of fresh air. If you have ever been aboard a ship, you would know that for some people, especially first-timers, the experience could be unpleasant, with motion sickness, feelings of suffocation, and symptoms of claustrophobia possibly creeping up on you during unexpected moments. This is where portholes can come in to save the day.

Third, most cruise liners and similar sea transportations units have affixed portholes in every living quarter to allow for a more pleasant and comfortable atmosphere, much like how normal rooms have windows of their own.

Why are Portholes Circular & The Benefits?

The design of portholes is singular primarily due to engineering genius and scientific findings. The explanation below would also serve to justify why other transportation crafts such as space shuttles, submarines, and airplanes have similarly shaped windows.

Portholes are subjected to a lot of pressure, whether it be from the wind, the seas, or other external elements.

When the port lights (the thick glass panels affixed to portholes) are designed with sharp edges and angles, rather than having an equal distribution of pressure throughout the panel, it would actually be the corners and edges that will absorb most of the force, which would essentially make the window more prone to damage, cracks, or outright shattering.

Should You Get a Porthole for Your Boat?

For all the reasons and justifications mentioned above, we would absolutely recommend that you get a boat that has portholes, or at the very least, have a few portholes installed in strategic areas throughout your vessel.

Think of how bleak and downright nerve-wracking it would be to stay in an area of the boat that does not allow natural light to come in, and also does not offer a view to the outside world (albeit in a limited capacity).

If you want to ensure that your boat experience is optimized, fun, and practical, then portholes are absolutely supposed to be part of the major list of considerations in buying a boat.


Owning a boat is a very sophisticated or intricate process, and acquiring knowledge such as this, although relatively minor in scope, will definitely aid you in deciding which boat to get, or at the very least, whether or not you should get a boat for yourself.

If anything, the next time someone asks you, “Why do boats have round windows,” you would definitely have much more to say than the average Joe. We hope you enjoyed this piece and maybe next time we could discuss the different sizes of portholes, and why normal windows are rectangular in size.

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