Standards-cited reference
California King and Standard King Dimensions: Exact Sizes from the ISPA Size Schedule
The International Sleep Products Association publishes a mattress size schedule that most US manufacturers follow. Under that schedule, King is 76 by 80 inches and California King is 72 by 84 inches. ASTM F1566-18 specifies typical manufacturing tolerances of plus or minus 0.5 inches.
Last verified April 2026
The two US Kings, side by side
| Size | Inches (W × L) | Centimetres | Square feet | Square inches | Source |
|---|---|---|---|---|---|
| California King | 72 × 84 | 182.88 × 213.36 | 42.0 | 6,048 | ISPA schedule[1] |
| Standard King | 76 × 80 | 193.04 × 203.2 | 42.2 | 6,080 | ISPA schedule[1] |
ASTM F1566-18 (Standard Test Methods for Innersprings) allows typical manufacturing variance of plus or minus 0.5 inches on both width and length[2]. Premium manufacturers typically hit within plus or minus 0.25 inches.
International size comparison
US Kings do not directly map to UK, EU, or Australian sizes. Sheet sets bought overseas often will not fit a US mattress and vice versa. UK "King" is closer in width to a US Queen.
| Name | Region | Inches (W × L) | Centimetres | Notes |
|---|---|---|---|---|
| California King | US | 72 × 84 | 182.88 × 213.36 | Longer, narrower |
| Standard (Eastern) King | US | 76 × 80 | 193.04 × 203.2 | Wider, shorter |
| Super King | UK | 70.87 × 78.74 | 180 × 200 | Narrower than US King, shorter than Cal King |
| King | UK | 59.06 × 78.74 | 150 × 200 | Closer to US Queen, NOT US King |
| King | EU continental | 62.99 × 78.74 | 160 × 200 | Varies by country (Spain, France, Italy) |
| King | Australia | 72.05 × 80.31 | 183 × 204 | Nearly identical to US Standard King |
UK and EU dimensions cross-checked against published national bedding size charts and CEN (European Committee for Standardization) reference materials.
Per-person sleep surface math
Width is what couples actually feel. The total area of both Kings is similar; the per-person width is not.
| Scenario | Cal King (72 wide) | Standard King (76 wide) |
|---|---|---|
| Solo sleeper | 72 in | 76 in |
| Two adults | 36 in each | 38 in each |
| Two adults + small dog (~12 in wide) | 30 in each | 32 in each |
| Two adults + medium dog (~18 in wide) | 27 in each | 29 in each |
| Two adults + one child (~24 in) | 24 in each | 26 in each |
Reference scale: 38 inches is approximately the width of a Twin XL mattress (ISPA spec: 38 by 80). 36 inches is approximately the width of a US military cot. Width matters more than most buyers think.
Diagonal length (for stair and doorway math)
Both King mattresses approach the limit of what a typical residential staircase carries. The diagonal of a rectangle determines whether you can rotate it through a tight turn.
California King
- Diagonal: 110.6 in (sqrt of 72² + 84²)
- 45-deg effective carry: ~92.7 in
Standard King
- Diagonal: 110.3 in (sqrt of 76² + 80²)
- 45-deg effective carry: ~78.0 in
Both exceed the IRC R311.7.1 minimum residential stair width of 36 inches. See shipping and moving for the full carry-path math.
Scale comparison vs other US sizes (ISPA schedule)
| Size | Width | Length |
|---|---|---|
| Twin | 38 in | 75 in |
| Twin XL | 38 in | 80 in |
| Full / Double | 54 in | 75 in |
| Queen | 60 in | 80 in |
| California King | 72 in | 84 in |
| Standard King | 76 in | 80 in |
Anchor reference for buyers upgrading from a Queen: a Cal King adds 12 inches of width and 4 inches of length over Queen. A Standard King adds 16 inches of width and zero length.
Tolerance and how to verify
ISPA dimensions are an industry standard, not a regulatory minimum. ASTM F1566-18 (the US standard for innerspring construction) specifies typical manufacturing tolerances of plus or minus 0.5 inches on both width and length[2]. A King mattress measured at 75.5 by 79.5 inches is within tolerance.
If you want to verify your mattress matches the schedule, use a metal tape measure across the top surface from seam to seam, ignoring rolled edges. Foam mattresses can compress when measured under hand pressure, so measure with the mattress unloaded.
Premium manufacturers typically hit within plus or minus 0.25 inches. Lower-tier compressed-foam mattresses may show slightly more variance, particularly in the first 30 days as the foam fully expands from its shipping compression.
Citations
[1] International Sleep Products Association mattress size schedule (industry standard reference for US mattress manufacturers). [2] ASTM F1566-18 Standard Test Methods for Innersprings in Mattresses; specifies tolerance ranges for innerspring components and typical manufacturing variance. International size data cross-checked against published UK, EU (CEN), and Australian retailer size charts.
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