How to Fill the Gap in a Split King Bed [Step by Step Guide]

Split king beds are comprised of twin XL mattresses pushed side by side, which produces an unsightly and uncomfortable gap in the middle. What can you use to fill in this gap?

To fill in the gap in a split king bed, try these solutions:

  • Tie the beds together
  • Use a king-sized fitted sheet
  • Try a gap filler
  • Add a bedframe
  • Install an anti-slip pad

In this guide, we’ll explain all your options for stuffing the gap so your split king bed can feel like one seamless mattress. There’s lots of great information to come, so check it out!

Comfortable hotel bedroom with split king bed, How to Fill the Gap in a Split King Bed [Step by Step Guide]

Five Solutions for Filling in the Gap in a Split King Bed

Tie the Beds Together

You can always tie the beds together to prevent the shift in mattress positioning that’s so unwanted with a split king bed.

You need a durable type of tie for this job, yet you have more versatility than you might expect.

For instance, you can use zip ties, a cord, or regular rope. Some particularly inventive people can even tie together belts, but this should only be used as a last resort.

All you need to do is take one single bedframe, push it against the other, and then use your rope of choice to secure both bedframes.

Voila, no more gap in your split king bed.

Use a King-Sized Fitted Sheet or Cover

Why not treat the twin XL mattresses like one king-sized mattress and put a fitted sheet or cover on top?

The tightness of the fitted sheet will prevent the mattresses from shifting away from one another, which tends to happen a lot when you and your partner are trying to sleep.

Try a Gap Filler

The most accessible and convenient measure for a king-sized bed gap is a gap filler such as this one.

Check out this gap filler on Amazon.

As the name suggests, a gap filler is a product designed to slot right into the gap between two twin-sized mattresses. It’s sometimes referred to as a bed bridge or a mattress wedge.

Made of soft, plush material with a foam shape, you put the gap filler foam side down.

The foam fills the gap between the two mattresses, while the other side of the bridge barely stands out from the rest of the bare mattress.

It’s soft and comfortable, so you won’t feel it while sleeping, and better yet, no more gaps!

A connector strap hooks underneath the mattress to ensure the gap filler doesn’t move out of alignment while you’re sleeping.

You can make your bed, put on sheets like usual with a gap filler, and sleep more soundly, knowing the two XL mattresses won’t move.

Add a Bedframe

Here’s another simple, efficient solution for filling a split king bed gap.

Push the two mattresses together exactly as you like them. Next, take a flexible measuring tape and calculate the length and width of the mattresses when united.

Now you need a bedframe that fits the exact measurements of your split king bed.

Once you insert the dual mattresses into the one frame, you’ll find that they should fit snugly side by side. Neither mattress can slip out of position, which prevents the space between them from widening.

Install an Anti-Slip Pad

Our final solution is this – buy an anti-slip pad [or use anti-slip straps].

An anti-slip pad is made of a grippable material that holds onto the bottom of both mattresses and prevents them from moving.

You put the anti-slip pad on the bedframe and the mattress on top. Otherwise, you’ll feel the pad over the mattress, which won’t be very comfortable.

Most anti-slip pads are trimmable with a regular pair of household scissors.

If you need two pads for your split king bed, you can always trim them down to the correct size, so the pads don’t droop over the sides of the bed frame.

Check out this anti-slip pad on Amazon.

Why Sleep in a Split King Bed?

Unmade bed in an unrecognisable hotel room

Although split king beds can be a little challenging to work with at times, they’re beneficial in various ways, so let’s take a look.

Less Motion Transfer

Are you awoken in the dead of night when your spouse or partner moves subtly in bed due to your proximity? Forget about when they roll over all the way. You always feel that.

A split king bed reduces the motion transfer rate due to the increased distance and the fact that each sleeper has their own mattress.

If your spouse or partner tosses and turns all night but doesn’t realize it, you don’t have to spend sleepless nights because of their movement. You won’t feel it nearly as much.

More Comfort Customization

Sure, you could buy one of those beds with adjustable firmness controls, but those can be expensive.

Your alternative is a split king bed. The two mattresses must be of the exact dimensions and do not have to share the same firmness levels.

You might prefer a very soft and squishy mattress while your partner or spouse can only sleep on a firmer, even hard mattress.

Now you can have your mattress preferences without worrying about disturbing the other.

More Space

A full-sized bed seems so large when you have it to yourself. Then your spouse or partner joins you in bed, and you feel like you’re sleeping on the edge of the mattress every night.

You regularly jockey for position and push and pull blankets all night to see who gets the bigger share.

If the presence of your partner or spouse prevents you from getting the full night’s sleep that you need, that’s another reason to consider a split king bed.

Rather than sleeping in separate bedrooms–which some couples feel is a death knell for their marriage or relationship–you can sleep in different beds but still be close to your partner or spouse.

You’re not that close anymore, and that’s precisely how you like it!

Why You Can’t Leave the Gap in a Split King Bed

Comfortable hotel bedroom


Is the gap in a split king bed that big a deal? If you try sleeping in a split king bed for long enough without any of the solutions from earlier, you’ll realize very quickly that, yes, it is.

Here’s why.

It’s Uncomfortable

Discomfort of any kind, notes Mayo Clinic, can keep you awake at night.

That includes the discomfort of feeling the gap underneath your back.

Sure, you could always roll over and sleep further away from the gap, but once you’re asleep, you have no control over your positioning.

You could find yourself back in the middle of the bed, feeling the gap from your head to your toes.

This can wake you up throughout the night, even more than your spouse or partner’s tossing and turning.

It’s such an easy fix that you’ll wonder why you sacrificed so many low-sleep or no-sleep nights to the gap between your twin XL mattresses!

You Could Wake Up with Aches and Pains

Man suffering from backache

It’s not only that the gap in a split king bed doesn’t feel good in the moment, but it could cause pain when you wake up the next morning.

You might find that you’re stiff and achy most days, especially in your back, which bears the brunt of the gap in the split king bed.

This isn’t pain you shake off as you get out of bed. It sticks with you.

Perhaps by the time you’re having your second cup of coffee and certainly by lunch, you need to take a painkiller to help you deal.

You Will Lose Things

Woman lost something under the bed

People bring lots of things to bed with them. If yours is a split king bed, many of those small items might not be seen again.

We’re talking earplugs, earrings, earbuds, condoms, and even rings if you’re not careful.

It’s not like the items fall into a black hole, but they might as well.

Right now, your items are trapped in between the mattresses or are stuck underneath the mattress on the box spring.

If not, the items fell straight to the floor under the bed, where it can be hard to see them.

You Might Fall Through

Once that gap opens between the two twin XL mattresses, it will expand as the night goes on, notes Sleeping Ocean.

You might be asleep by this point, so you don’t even realize what happens until you slip through the gap.

As a grown adult, the chances of you falling all the way through are low, but if you fall even halfway off the bed, that’s going to scare the daylights out of you.

If you have a child or pet who shares the bed with you, they’re much more likely to fall through, and we mean all the way through.


Filling the gap in a king-sized bed needn’t be difficult when you have so many options. A gap filler is chiefly recommended among them.

You and your spouse or partner will get a better night’s sleep with these solutions, so try them tonight!

Before you go, don’t miss this fantastic content:

3 Inch Vs. 4 Inch Mattress Toppers: Which To Choose?

Can You Use a Memory Foam Mattress on a Futon or Daybed?

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