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SleepSetupCalc

Sizing and fit

Split Size Decision Calculator

Last updated Researched from published specifications and owner reviews, not tested in person

Quick answer

Whether a split king or split California king is worth it for your setup.

Whether a split king or split California king is worth it for your setup. The formula is shown under the calculator, and every figure it uses is labelled as either an industry standard or a convention, so you can see which parts are settled and which are guidance.

Calculator Industry standard figures

Result

Split is worth it

two twin XL

Split king footprint
76 by 80 in, two 38 by 80 halves
Standard king footprint
76 by 80 in, one piece
Reasons in favour
2

A split king lets each side incline and be a different firmness. The tradeoff is the gap down the middle, which needs a split-king sheet set or a gap filler.

The formula

A split king is two twin XL mattresses side by side, 38 by 80 in each, 76 by 80 in combined: the same footprint as a king.

Products for this answer

These re-order as you change the numbers above. Prices change often.

Frequently asked questions

How does the split size decision calculator work?

A split king is two twin XL mattresses side by side, 38 by 80 in each, 76 by 80 in combined: the same footprint as a king. The calculation runs in your browser as you type, and the working is shown line by line beside the result so you can check it against your own measurements rather than taking the number on trust.

Are these figures an industry standard or a convention?

These are published industry standards. US mattress dimensions, fitted sheet pocket classes and box spring profiles are consistent across manufacturers, so the figures here are the same wherever you shop. That makes them safe to measure and order against, though you should still confirm the exact dimensions a specific product publishes before buying.

What happens if I enter numbers outside the usual range?

It stops and says so rather than guessing. When the inputs fall outside what the published data supports, the result reads "Not enough to answer" instead of showing a confident figure. A disclaimer does not make a wrong number right, so returning nothing is the honest outcome when the underlying data does not cover your case.

Does this calculator store the numbers I enter?

No. Everything is computed in your browser and nothing you type is transmitted or saved. There is no account, no login and no record of your measurements. You can block cookies entirely and every calculator on this site will still work exactly the same way.

How to read the numbers on this page. Standard mattress and bedding dimensions are industry-wide and the same across manufacturers. Guidance like replacement intervals, firmness by body weight and walking clearance is convention rather than a measured standard, and every table here says which it is. Where a manufacturer does not publish a figure we leave it out instead of estimating. This is not medical advice: a mattress is not a treatment for a medical condition, and persistent pain is a reason to see a clinician.