72 inches wide. 84 inches long. Those two numbers decide whether a Cal King is your dream bed or an expensive mistake. Here's every measurement that matters — mattress, frame, room, doors and bedding.
The California king mattress is 72 inches wide by 84 inches long (183 × 213 cm), with 6,048 square inches of surface. It is the longest standard mattress sold in the US — 4 inches longer and 4 inches narrower than a standard king (76" × 80"). Typical thickness: 10–14 inches for modern foam and hybrid models.
The frame adds 2–6 inches per side for rails, plus headboard height. Expect a typical Cal King footprint of roughly 76–78" wide × 88–92" long, and headboards 40–60" tall. Upholstered and canopy frames run largest; simple metal platforms run smallest. Always check the listed assembled dimensions, not the mattress size.
A 12' × 12' bedroom fits a Cal King with nightstands and walking space. The math: 84" bed length + 24–30" walking clearance at the foot + nightstands (~20" each side of the 72" width) ≈ 11–12 feet in each direction. Smaller than 11' × 11'? The room will feel cramped — consider a queen instead.
An 84"-long frame (or its box) must travel from your front door to the bedroom. Measure the narrowest point: door frames (typically 30–36"), hallway turns, and stairwell landings. Most Cal King frames ship in multiple boxes precisely for this reason — check box dimensions in the listing before delivery day.
Buy only bedding labeled "California King": fitted sheets 72" × 84" (deep pocket 15"+ for thick mattresses), flat sheets ~108" × 102", comforters ~104" × 96" or larger, and bed skirts to match your frame height. Standard king bedding is 4" too wide and 4" too short — it will never stay put.