How to Properly Convert Twin XL Mattresses into a King

Last Updated on March 30, 2023

Sharing the bed with a partner is difficult for some couples.

This is especially true if one (or both) moves around a lot, and if one partner (or both) is a sensitive sleeper. This can become a big problem, and lead to a significant lack of sleep.

Many couples solve this issue by connecting two Twin XL mattresses to form a King sized mattress. With each partner having his or her own mattress to sleep on, it almost entirely solves the problem.

Almost entirely, but not quite.

Joining two Twin XL mattresses together provides a King-sized sleeping surface, and greatly reduces what you feel when your partner moves, or shifts. The problem with this solution occurs in the middle.

When two mattresses are joined together, it creates two problem areas:

  1. The “gap” in the middle can be annoying at best, and downright uncomfortable at worst. For couples that like to cuddle, this is often a significant inconvenience. 
  2. Two individual mattresses tend to move independently of one another. While this is a good thing when it comes to sleep, it can be quite awkward during sexual activity.


The solution

So, the best solution to this problem that we have found is the Bed Doubling System from Easy King.


the Easy King bed doubling system


The Easy King Bed Doubling system, essentially solves both of those problems via a center gap filler and a strap that secures both mattresses together.

The gap filler fills the opening in the middle. And the strap keeps the mattresses from shifting or coming apart. The entire setup takes less than 5 minutes to complete.

It’s an all-in-one solution that actually works!



Not just for sensitive sleeping couples

The bed doubling system is not just a solution for couples who are frustrated with their dual Twin mattress set up.

It’s also great for 2nd story bedrooms with narrow stairwells that are impossible to fit a King sized mattress through. 

This system also offers versatility for guest rooms. You don’t always know who will occupy your guest room. It might be two children, it might be a couple, etc.


two Twin XL beds side by side

If you have two Twin XL mattresses in your guest room, the bed doubling system allows you to easily alternate between two Twin XL mattresses or a King mattress.


How it works

Let’s take a look into how and why the Bed Doubling system functions, and how you can get the most out of it. While this should work seamlessly for most couples; by testing this product out thoroughly, we’ve found a few areas that can be optimized.

The Bed Doubling System from Easy King consists of three components:

  • The gap filler
  • The pad
  • The strap


The gap filler

The first step is to place the gap filler in the seam between both mattresses. The filler essentially fills the gap, so you no longer have that uncomfortable valley in the middle.


the bridge of a bed doubling system


While this does add a small additional layer in the middle, we have a fix for that later on in this article.

The gap filler is about 10″ wide, so about 5″ on each side of the mattress. You can definitely feel it if you’re looking for it, but most people won’t even realize that it’s there because of the next part…


The fabric

The next layer is the fabric that goes over the gap filler. It attaches to the filler gap via Velcro.

The fabric serves two purposes:

1.) It creates a smoother transition between the gap filler and the mattress.

2.) It helps keep the gap filler securely in place via the strap that goes around both mattresses.


the gap filler for a bed doubling system


The fabric is an essential part of the system, as without it, the edges of the gap filler would be much more apparent. Also, without the fabric, there is nothing to hold the gap filler in place, and it can shift and move around.

So, the fabric is the glue that holds the entire system together.


The strap

The strap is the final piece of the puzzle, and puts everything together.

It goes around the entire length of the mattress, and loops through the top fabric that covers the gap filler:


the buckle for a bed doubling system


The strap holds the fabric tightly in place, putting downward force on the filler gap. It also holds both Twin mattresses securely together to prevent them from moving around as well.

The strap has a buckle, and you basically tighten it – like a belt.



Care instructions

The entire system is machine washable and dryable. You can throw the entire system in with the sheets every time you do a wash.


Recommendations to optimize this system

While this system works seamlessly for most people, we do have a few guidelines to follow, and a few recommendations. These suggestions should get the most out of this system, and provide you with the best results.



If you were previously using two individual Twin sized fitted sheets, you’ll have to switch to a King sized fitted sheet now.

Two Twin sheets will not fit over the mattresses with the system in place – unless you put the sheets on first, which tends to be a hassle every time you change the sheets.


a sheet set on a bed



Mattress pad

To make the bed as comfortable as possible, we would suggest adding a mattress pad on top of the bed, under the fitted sheet. While the gap filler and top fabric aren’t very noticeable, you can still slightly feel their presence.


a mattress pad on a bed


Adding a mattress pad on top makes them practically disappear. Unless you look underneath, you’ll never even know that they are there.

A memory foam topper would definitely work as well.


Buckle positioning

Position the strap so that the buckle is either at the foot of the bed or on the sides. 


how to position the buckle for a bed doubling system


If you’re like most people, then the head of your mattress will be against a wall. If the buckle is in direct contact with the wall, it can prematurely wear out your fitted sheet, and or scuff the walls.


It will not work with an adjustable bed

Depending on your adjustable setup, the strap will either pop off completely or make your mattress bend or contort in awkward positions. This system is not compatible with adjustable beds.


Final thoughts

The bed doubling system from Easy King definitely solves the issues created by joining two Twin XL mattress together to form a King bed.

It not only fills the gap in the center, but also holds both mattresses securely in place.

We have tested out other similar products, but they usually fail in one of, if not all three areas:

  • Made of cheap materials
  • The center gap filler sticks out like a mountain
  • No strap to hold everything in place

This system is made well (and includes a 5-year warranty), has an almost seamless transition between the filler and mattresses, and includes the strap.

It just plain works.

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