Some common questions that come to mind when thinking about bidet toilet seats are:  how big is the opening of the seat? Does having a bidet seat mean you must sacrifice seating area size? To the naked eye, it certainly does seem that way, but is this fact? Below we will discuss these seating area issues for both round and elongated bidet seats.

Average dimensions of the seat opening for:

Bidet Seats

  • Elongated: 11.5”L x 8”W
  • Round: 10”L x 8”W

Diagram of a round, and elongated bidet's seating area dimensions


Regular Toilet Seats

  • Elongated: 12”L x 8”W
  • Round: 10”L x 8”W

Diagram of a round, and elongated toilet seat's seating area dimensions

As you can see, the differences of the opening sizes between a bidet seat and a normal toilet seat are barely noticeable.  However, when you actually sit on a bidet seat it will seem smaller than a standard toilet seat. Why is this?

Well it’s not so much that the opening of the seat itself is smaller, but that the total seating area all around your bidet’s seat is smaller than your conventional toilet seat. This in turn makes the bidet seat opening size seem smaller, although in reality it is only half an inch smaller than your conventional toilet seat opening.

So why is the total seating area on a washlet smaller? Well, it’s because bidet toilet seats need a section behind the actual seat to store all of its electronic and mechanical parts.  As a heavy duty appliance, washlet bidet seats need quite a bit of space to store its various internal components including:  a water heating system, printed circuit boards, air pump, solenoids, warm air dryer fan, etc.  There’s also a 6-8” nozzle assembly and many other things take up quite a bit of space in a bidet seat. 

Alpha and Brondell Bidet side by side, with open lids depicting seating area

*The rear portion behind and underneath the seat stores the internal components

All of these various parts are stored in the main body of the bidet toilet seat, behind the actual seating area itself.  The amount of space needed for all of these components is pretty standard across the industry.  This means that there’s not much variance in seating area between the various brands and models of bidet seats – maybe a ½” at most.  Also, the rear of most bidet seats tend to slope upwards for the last inch or so. This often makes the seat feel smaller than it actually is. At the end of the day, when considering a bidet seat, you will need to sacrifice a bit of seating area, but the features packed in a bidet seat are definitely worth it.

So why can’t they make the bidet seat’s seating area bigger to accommodate for the space taken up by all the mechanics in the rear portion? Well this one is simple. They would not fit on your toilet. Mounting a bidet toilet seat as currently constructed can already be a snug fit for a handful of toilets. If you were to add more seating area, mounting the bidet seat on a typical residential toilet would be an impossible task.

So is there a particular bidet seat model or brand with a bigger opening or overall bigger seating area? The simple answer is no. All bidet seat openings are all very closely in the vicinity of 11.5 by 8.5 inches for elongated, and 9.5 by 8 inches for round, give or take a sixteenth of an inch, which won’t do much for anyone. The good news is that your sacrifice in sitting area is well worth it in the end once you’re getting that good clean feeling from your new bidet seat.