What distinguishes it
A distinct US format that trades four inches of King width for four inches of added length.
It is narrower and longer than a regular US King, so the names are not interchangeable for frames or bedding.
72 × 84 in
Metric182.9 cm × 213.4 cm
Imperial72 in × 84 in
Surface area3.90 m²
Market aliases: Cal King, Western King.
-10.2 cm width · +10.2 cm length · -0.5% area
The area percentage uses US King as its denominator. It is narrower and longer than a regular US King, so the names are not interchangeable for frames or bedding. That difference can change whether a rigid frame opening or fitted bedding matches.
Not the same worldwide
It is close to an Australian King in width but more than 10 cm longer.
Evidence type: convention · high confidence.
Before ordering
A named size is not a fit guarantee. Compare the seller’s finished width, length and stated tolerance with the frame opening and bedding specification.
Published tolerance: Nominal convention; check finished dimensions.
Measure the finished mattress and the frame’s internal opening. Measure the mattress correctly and check which frame dimension controls fit.
Continue this decision
Evidence for this answer
- Better Sleep Council — Mattress SizesChecked 27 August 2026. Minimum factual dimensions only; original wording, tables and visuals.
Correction route: If a current source or product specification conflicts with this page, send the page URL and evidence through the corrections process.