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Split King mattress dimensions

A Split King is two Twin XL mattresses placed side by side in one frame.

Published by BedFit Atlas · Updated 2026-10-17

Dimensions at a glance

US · Nominal bed dimensions
Size	Width (in)	Length (in)	Area (sq ft)
Split KingReviewed 2026-10-17	76	80	42.2

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1. Split King

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A Split King is two Twin XL mattresses placed side by side in one frame. In the cited US profile each Twin XL is 38 by 80 inches, so the combined footprint is 76 by 80 inches: the same width and length as a standard King. In centimetres that is 193.0 by 203.2, and the combined area is 6,080 square inches, about 42.2 square feet.

Why split a King

The two halves can be different mattresses, so each sleeper can choose a different firmness or model. Split Kings are also the usual pairing for adjustable bases that raise the head or foot on one side only. Because each half is a Twin XL, a single half can be moved through doors and stairways more easily than a one-piece King.

Split King compared with King

Room planning is identical to a King: the assembled footprint is the same 76 by 80 inches. Consider a 12 ft by 12 ft room, with the mattress length aligned to the room length, both sides open, one 20 by 20 inch nightstand, and side and foot clearances each set to 24 inches. Both King and Split King require 144 inches across and 104 inches along, which leaves exactly zero inches across in a 144-inch room and 40 inches along. Zero remaining margin means any frame projection or measurement error makes the layout not fit; a 13-foot room leaves 12 inches across. These clearances are adjustable preferences for the worked example, not standards.

Bedding and the centre line

A Split King uses two Twin XL fitted sheets and one King-size flat sheet, duvet or comforter. The join between the two mattresses runs down the centre of the bed, and the halves can drift apart on a flat foundation unless the frame or a strap holds them together. Check that an adjustable base, if used, is sold as a split model.

Check both orientations, nightstands and the walking space you want.

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Sources and review dates

Data reviewed 2026-09-18.

Bed Sizes and Mattress Dimensions: Guide + Comparison Chart — Purple Purple, Bed Sizes and Mattress Dimensions: Guide + Comparison Chart; numerical reference values, not product measurements or universal tolerances.
Published room-fit geometry, version 1 — Bed Dimensions