Standard U.S. mattress sizes range from a twin at 38 × 75 inches to a California king at 72 × 84 inches. A queen is 60 × 80 inches, while a standard king is 76 × 80 inches. These measurements describe the mattress, not the complete bed frame. Use the chart to narrow your choices, then check the exact product specifications before ordering.
What are the standard mattress dimensions?
The chart below gives width first, then length. Centimeters are calculated from the listed inches using exactly 2.54 centimeters per inch, rounded to one decimal place. They are conversions of nominal U.S. sizes, not a separate international sizing standard.
| U.S. size | Width × length, inches | Width × length, cm |
|---|---|---|
| Twin | 38 × 75 | 96.5 × 190.5 |
| Twin XL | 38 × 80 | 96.5 × 203.2 |
| Full / double | 54 × 75 | 137.2 × 190.5 |
| Queen | 60 × 80 | 152.4 × 203.2 |
| King | 76 × 80 | 193.0 × 203.2 |
| California king | 72 × 84 | 182.9 × 213.4 |
These nominal dimensions match Helix’s manufacturer size reference. Specifications can differ: Casper’s size guide lists its full/double at 53 × 75 inches. A familiar size name is therefore a starting point, not a guarantee of an exact fit.
How do twin, twin XL, full and queen compare?
Twin XL keeps the twin’s nominal 38-inch width and adds 5 inches of length. Two ordinary twins do not become a standard king: together they measure 76 × 75 inches, leaving the arrangement 5 inches shorter than a king. Check the “XL” in a listing rather than relying on a photograph.
Using the chart’s dimensions, a full is 16 inches wider than a twin but the same length. Moving from full to queen adds 6 inches of width and 5 inches of length. That change also affects the frame, fitted sheet and mattress protector. Reusing a full-size accessory on a queen is not a dependable way to save money.
Is a California king bigger than a king?
A California king is longer but narrower: 4 inches longer and 4 inches narrower than a standard king. The standard king has slightly more surface area, 6,080 square inches compared with 6,048. “California” does not mean wider, and the two sizes do not use interchangeable fitted sheets.
Choose between their actual rectangles rather than the names. If a room has limited width beside the bed, the narrower California king may leave more side space, but its extra length takes space from the foot of the bed. Both effects matter when a dresser or doorway sits opposite the footboard.
What size is a split king?
A typical U.S. split king uses two twin XL mattresses, each 38 × 80 inches, side by side. Together they form the nominal 76 × 80-inch king footprint. Confirm both pieces are included: listings may show a pair while the selected price applies to one mattress.
Also check the compatible base and bedding. Two separately moving mattresses generally need separate fitted sheets, and a standard king sheet set may contain only one. Split California king is a different configuration; never substitute twin XL pieces simply because the listing includes the word “split.”
Why can the actual mattress measure differently?
Mattresses are upholstered products rather than precision-cut room dividers. Helix states that its handmade mattresses may vary by up to 2 inches on a given side. That is the manufacturer’s stated allowance, not a universal tolerance for every brand. Ask the seller about the selected model if a close fit matters.
Remove bedding before measuring. Measure straight across the widest part and from head to foot, keeping the tape level rather than following a curved quilted edge. Record depth separately. For a newly unpacked compressed mattress, follow the manufacturer’s expansion instructions before judging the finished measurements.
How much space does the bed frame need?
A queen mattress may be 60 × 80 inches, but a queen bed’s outside dimensions can be larger because of side rails, upholstery, a headboard and a footboard. Find both the mattress opening and the assembled frame’s maximum width and length. Include any headboard that projects beyond the rails.
Mark the frame’s outside rectangle on the floor with removable tape suited to the surface. Open doors, closet doors and drawers fully, then walk the routes you use. If you plan to store things beneath the bed, check both vertical clearance and the space needed to pull them out. Our under-bed storage guide covers that separate access check.
Treat mattress height as another measurement, not a feature implied by “queen” or “king.” Add any topper when checking fitted-sheet pocket depth. The sheet fit and fabric guide explains what to compare on the package.
Are mattress names the same in every country?
No. For example, TEMPUR’s U.K. king-size range identifies a standard king as 150 × 200 centimeters, substantially different from a U.S. king. European variants may also appear within a national retailer’s catalog. Compare numeric measurements, country and product model whenever ordering imported mattresses, frames or bedding.
What should you check before ordering?
Keep a short measurement record: mattress width, length and depth; frame outside dimensions; doorway and stair clearance; and packaged delivery dimensions. A box that reaches the bedroom does not prove an expanded mattress can later leave it. Check the delivery method and the manufacturer’s handling restrictions instead of assuming the mattress can be folded.
Finally, review the selected size at checkout, the included pieces, compatible support requirements and return conditions. Save the product specification page with your order. This turns a vague “king-size” purchase into a set of measurements you can check when it arrives.
Sources and measuring supplies
Primary references: Helix mattress dimensions and tolerance, Casper mattress-size guide, and TEMPUR U.K. king dimensions. Check the current specification for the particular model you are buying.
For measuring tools, browse retractable tape measures on Amazon. Compare reach, units and readability before choosing one.
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