If you and your partner fall into different weight groups (under 130, 130–230, over 230 lb), buy two twin XL mattresses as a split king. With Helix: Midnight for lighter side sleepers, Dusk for back and stomach sleepers, Plus for anyone over 230 lb.
- A split king is two 38-inch twin XLs: together 76 by 80 inches, exactly a king.
- It works flat on your existing king frame; an adjustable base isn't required.
- Helix Plus is the only Helix model with a published weight limit: up to 1,000 lb.
- Two base models together came to about $1,680 on sale; a Midnight plus a Plus about $1,800.
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If you wake up with a sore back and your partner thinks the bed is fine, it's probably not a bad mattress. It's that you don't weigh the same. How firm a mattress feels comes down to how far you press into it: the heavier person presses through the soft layers onto the firm part underneath, while the lighter person never gets past the top. Put a 200 lb and a 130 lb person on one bed and they won't agree on firmness, and both are right.
You don't have to compromise. Instead of one mattress, buy two smaller ones side by side, taking exactly the space of a king, so each of you sleeps on the bed built for your body. That's a split king, and here's how to build one with Helix.
Quick verdict
Two lighter sleepers in different groups (one under 130, one between 130 and 230): a Helix Midnight and a Helix Dusk. If one of you is over 230 lb: a Midnight or Dusk on the lighter side and the Helix Plus on the heavier. And if the heavier partner sleeps on their side, make their side the Plus whatever their group. Two twin XLs, on the frame you already own.
The 30-second test
Three weight groups decide everything in this category: under 130 lb, 130 to 230 lb, and over 230 lb. Work out which group each of you is in. If you land in different groups, you've just been told to buy two different mattresses; if you land in the same group, one good bed will do. You'll see people online say a split king starts making sense once you're 50 or 70 lb apart. Those numbers are made up; the three groups are what the industry actually builds around.
What a split king is
Two twin XL mattresses, 38 inches wide each. Pushed together they make 76 by 80 inches, a king to the inch, so they go on the king frame you already own. It does not need an adjustable base; that's the upsell, and it works flat.
Two small things to budget for: a seam runs down the middle, which people fix with a T-shaped connector between the halves or a king-size pad over the top. For bedding, a split king sheet set is two twin XL fitted sheets and one king flat sheet, though ordinary king sheets fit fine since it's the same 76 by 80.
Under 230 lb, side sleeper: Helix Midnight
Built mainly for side sleepers. Memory foam over softer polyfoam lets your shoulders and hips sink in a little instead of taking all the pressure, and up to 1,000 individually wrapped coils underneath keep your spine straight. Helix rates it 6 out of 10, and on a lighter body that's exactly right, because you press into the comfort layers rather than lying on top of them. Back sleepers at this weight are fine on it too; the coils hold you level and you just sink less.
130–230 lb, back or stomach sleeper: Helix Dusk
Built for back and stomach sleepers, with the same coil system underneath (up to 950 wrapped coils). The difference is the top: instead of memory foam it uses what Helix calls dynamic foam, which is springier, so you sit more on the bed than in it. Helix rates it a 6 like the Midnight, but it isn't. Lying on them one after the other, the Dusk is a 7 and you feel it immediately. You press in about an inch and three-quarters, the least of the three beds, which is what a back or stomach sleeper wants.
Over 230 lb: Helix Plus
The only bed in Helix's range with a published weight number: up to 1,000 lb. It has extra-dense 4 lb-per-cubic-foot memory foam on top (the kind that holds its shape instead of developing a dip), a firm transition layer, and taller wrapped coils with a reinforced edge so the sides don't collapse when you sit. We put real weight on it and nothing gave, in the middle or at the edge; sitting on the side, it barely moves, the best of the three by a long shot.
One exception to the groups: if the heavier partner is a side sleeper, the Dusk is too firm for them. Their shoulders won't sink in far enough, so put them on the Plus instead.
Prices, trial and warranty
All three beds are 11.5 inches tall, so pushed together the tops line up flat, with no ridge to roll into. They're made in the US with CertiPUR-US certified foam.
| Twin XL | Retail | On sale (at time of review) |
|---|---|---|
| Helix Midnight | about $1,120 | about $839 |
| Helix Dusk | about $1,120 | about $839 |
| Helix Plus | about $1,250 | about $937 |
Two base models together came to about $1,680 on sale; a Midnight and Plus combo about $1,800.
- Trial: 120 nights, keeping it at least 30 before a return. After that, Helix arranges pickup at no cost.
- Returns limit: Helix allows up to two returns per household, ever, so with two beds you have exactly one swap each. Get the sides right first time.
- Warranty: limited lifetime, full coverage for 10 years then prorated, covering dents deeper than 1.5 inches and cover or stitching faults. Slats more than 5.5 inches apart void it.
- Not included: no published weight capacity for the Midnight or Dusk, and old-mattress removal is a separate service from about $219 (free in California).
If you're staying on a queen
Helix doesn't make a split version for a queen, and almost nobody does, because a queen is too narrow to split into two real mattresses. The one bed we know that solves it is the Sleep Number Solaire: an air mattress under foam and latex, where each side sets its own firmness with a remote, from queen size up, at about $4,800 for a queen. All that foam and latex softens what the air chamber is doing, so the gap between softest and firmest settings is narrower than the remote suggests. Expect an adjustment, not two different mattresses. Otherwise, moving up to a king is what makes this work.
Pros and cons
What works
- Each partner sleeps on a mattress built for their weight.
- Uses your existing king frame; no adjustable base needed.
- Matching 11.5-inch heights mean no ridge in the middle.
- Free pickup on returns after 30 nights.
What doesn't
- A seam down the middle needs a connector or a pad.
- Only two returns per household, ever.
- No published weight limit for the Midnight or Dusk.
- Doesn't work on a queen without a specialist bed like the Solaire.
Frequently asked questions
When should a couple get a split king?
When the two of you fall into different weight groups: under 130 lb, 130–230 lb, or over 230 lb.
Does a split king need an adjustable base?
No. Two twin XLs make exactly a king (76 by 80 inches) and work flat on a regular king frame.
Which Helix is best for a heavy side sleeper?
The Helix Plus. The Dusk is too firm for a heavier side sleeper's shoulders.
Can you split a queen mattress?
Not really; a queen is too narrow for two real mattresses. The Sleep Number Solaire sets firmness per side, but the range is narrower than it sounds.
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