Best mattress for a split king

A split king is two twin XL mattresses, so you shop for two twin XLs, not one king.

Short answer: a split king is two twin XL mattresses (38 × 80 in each) side by side, 76 × 80 in in total, the same as a king.^{[1 · Nov 11, 2026]} Buy two twin XLs of the same height so the surface stays even, or one king if you don't need separate sides.^{[1 2 · Nov 11, 2026]}

Two parents, two young children and a golden retriever laugh together on a king bed in a bright bedroom with a beamed ceiling and big windows

Split king vs king at a glance

Setup	Dimensions	Who it fits
Split king (2 × twin XL)	2 × (38 × 80 in) = 76 × 80 in^{[1 · Nov 11, 2026]}	Couples who want different firmness, or an adjustable base where each side moves on its own^{[1 · Nov 11, 2026]}
King	76 × 80 in^{[2 · Nov 11, 2026]}	Couples who prefer maximum space; couples sharing with a child^{[2 · Nov 11, 2026]}
One twin XL	38 × 80 in^{[2 · Nov 11, 2026]}	Single adults over 6 ft; teens^{[2 · Nov 11, 2026]}

Options to look at

Zinus 10 Inch Twin XL Green Tea Memory Foam Mattress, Medium Firm Feel: a 10 in twin XL memory foam mattress (two make a split king).
Novilla 10 Inch Twin XL Mattress, Gel Memory Foam Mattress Twin XL Size: a 10 in twin XL gel memory foam mattress (two make a split king).
Zinus 10 Inch King Green Tea Essential Memory Foam Mattress, Medium Feel: a 10 in king, if you'd rather have one piece with no seam.

These are options to look at, not a tested ranking. We haven't slept on them. Each one is described only by what its Amazon listing title says; check the listing's dimensions, materials and return terms before you buy.

What to check before you buy

Same height on both sides: both twin XLs above are listed as 10 in; mixing heights leaves a step in the middle.
Sheets: a split king sheet set usually has two twin XL fitted sheets and one king top sheet.^{[1 · Nov 11, 2026]}
The seam: lying flat you usually shouldn't feel it; a king topper can cover a dip.^{[1 · Nov 11, 2026]}
Base: a standard king frame or foundation works, or a split king adjustable base.^{[1 · Nov 11, 2026]}

More on king vs two twin XL, king vs California king and sheet sizes.

Questions people ask

What mattress do I need for a split king?

Two twin XL mattresses, 38 × 80 in each, which together measure 76 × 80 in, the same as a king.

Can I use two different mattresses for a split king?

Yes, that's a main reason people choose a split king: each side can have its own firmness. Pick two with the same height so the surface stays even.

Sources: 1. Sleep Foundation, What is a split king bed?. 2. Sleep Foundation, Mattress sizes and dimensions guide. Checked Nov 11, 2026. Trademarks belong to their owners; figures are restated in our own words and tables, not reproduced.