Updated April 2026
Split King Mattress
A Split King is two Twin XL mattresses (each 38" x 80") placed side by side on a King frame. Total dimensions equal a standard King: 76" x 80". Each partner sleeps on a fully independent surface.
Each Side
38" x 80"
Twin XL per person
Combined
76" x 80"
Same as Standard King
What Exactly Is a Split King?
A Split King consists of two separate Twin XL mattresses (38" x 80" each) placed side by side on a King-size foundation or adjustable base. The total sleeping surface is identical to a standard King: 76 inches wide by 80 inches long.
The defining feature is independence. Each side can be a different mattress, different firmness, different material, even different brand. More importantly, when used with a split adjustable base, each side can be raised or lowered independently. One partner can elevate their head for TV without disturbing the other.
The gap between the two mattresses is typically 1-2 inches. Most couples report not noticing it while sleeping, though some find it annoying when rolling toward the center. Gap-filling toppers are available to smooth the seam.
Pros and Cons
Pros
- +Each partner can choose a different firmness level
- +Adjustable bases allow independent head/foot positioning
- +Zero motion transfer between the two sides
- +Great for couples with different sleep positions or health needs
- +Easy to move, two 38" halves vs one 76" mattress
- +If one side wears out, replace only that half
Cons
- -Gap down the middle of the bed (most couples don't notice it)
- -More expensive than a standard King (roughly 1.5-2x)
- -Sheets need to be designed for Split King (standard King sheets don't stay put without gap filler)
- -Adjustable base required to get the full benefit, otherwise the gap is the only advantage
- -More complex setup and delivery
- -Not ideal for couples who sleep close together (the gap can be annoying)
Who Actually Needs a Split King?
Couples with very different firmness preferences
Strong use caseIf one partner wants a plush mattress and the other a firm one, a Split King solves the problem completely. Each side is an independent mattress. This is the primary use case.
Snoring or sleep apnea
Good use caseElevating the head by 30-45 degrees can reduce snoring. A split adjustable base lets the snorer raise their side without the partner doing the same. If snoring is disrupting your relationship, this is a legitimate solution.
Acid reflux or back issues
Good use caseElevated sleeping positions help with GERD and certain back conditions. Split adjustable lets one partner address a medical need without affecting the other.
Very different sleep schedules
Moderate caseA Split King reduces motion transfer to near zero. One partner coming to bed 3 hours later will not wake the other. Though a high-quality standard King with good motion isolation (foam or latex) can achieve similar results at lower cost.
Wanting to try a new mattress without both upgrading
Weak caseYou can replace just one Twin XL if one person's side wears out before the other. Cost-effective in theory, though matching sizes and compatibility with the base can be tricky.
Split King Adjustable Base Prices
The adjustable base is where most of the cost is. Without it, you are just getting two separate mattresses with a gap.
Sleep Number (i8 FlexFit 3)
Includes smart sensors, air chambers, zero-gravity mode
~$7,800 per side
Saatva Solaire
Add adjustable base separately. Cal King option available.
~$4,195 mattress only
Tempur-Pedic LUXE ADAPT + ERGO Extend
Includes Tempur-Ergo adjustable base, massage, anti-snore mode
~$8,500 total
Purple + PowerBase
Purple 4 mattresses + PowerBase adjustable base
~$3,000 total
Helix Midnight Luxe + Adjustable
Helix adjustable base with dual zones
~$3,500 total
Lucid + Adjustable Base (Amazon)
Budget option. Basic incline adjustment only.
~$1,200 total
Budget path: Two Zinus or Lucid Twin XL mattresses ($150–$200 each) on a budget adjustable base ($300–$500) will give you the full Split King functionality for $600–$900 total. Not luxurious, but fully functional for couples testing if split sleep works for them.
Sheets and Bedding for Split King
You cannot use standard King sheets
Standard King sheets are one piece. On a split base that articulates independently, they pull off. You need Split King fitted sheets, one per side, plus a standard King flat sheet on top.
Gap fillers prevent the seam problem
A foam gap filler wedge ($20–$50) bridges the 1-2 inch gap between mattresses, eliminating the dip in the middle. Most Split King sleepers use one.
Duvet covers work normally
A King-size duvet or comforter covers both sides normally. The gap is a fitted sheet problem, not a duvet problem.