A standard king mattress measures 76 inches wide by 80 inches long (193 cm x 203 cm), making it the widest mattress size sold in the United States. If you’ve been searching “what dimensions is a king mattress,” that’s the short answer — but the full picture involves inches, feet, centimeters, room requirements, and how a king actually compares to a queen or California king in real life.
This guide breaks down every measurement you’ll need before buying a king size bed, plus how it fits into your bedroom space, who it’s best suited for, and how it stacks up against every other standard mattress size.
What Dimensions Is A King Mattress In Inches
The core answer to king mattress dimensions is simple: 76 inches wide x 80 inches long. That’s the number printed on every U.S. mattress tag labeled “King” or “Eastern King” — the two terms are used interchangeably at nearly every major retailer.
Here’s what those inches mean in practice:
- Width: 76 inches — 16 inches wider than a queen
- Length: 80 inches — the same length as a queen mattress
- Sleeping surface: 6,080 square inches — nearly double a twin bed’s footprint
Each partner sharing a standard king mattress gets roughly 38 inches of personal width — essentially a twin bed’s worth of space per person. That’s the number that tends to sell people on the size once they hear it, because it reframes the king from “a bigger bed” into “two bed’s worth of comfortable sleeping space” pushed together.
“A king isn’t just a bigger queen — it’s the only standard mattress size that gives two adults roughly a twin bed’s width each.”
Manufacturers do allow small variances. Most brands build to 76″ x 80″, though you’ll occasionally see listings at 76″ x 79.5″ — a half-inch difference that won’t affect bedding fit but is worth knowing so you’re not surprised by the fine print.
What Dimensions Is A King Mattress In Feet
Converted to feet, a king mattress measures 6 feet 4 inches wide by 6 feet 8 inches long. Feet-based measurements are often easier to picture when you’re planning a bedroom layout with a tape measure in hand, rather than doing inch-by-inch math against your walls.
What Dimensions Is a King Mattress in Feet
| Measurement | Feet | Inches |
|---|---|---|
| Width | 6’4″ | 76″ |
| Length | 6’8″ | 80″ |
If you’re mentally mapping the bed against your room, remember this measurement is for the mattress only — a bed frame or headboard typically adds a few inches beyond the mattress footprint on each side.
What Dimensions Is A King Mattress In Cm
For anyone working from metric blueprints, furniture imported from overseas, or simply more comfortable thinking in centimeters, a king mattress measures 193 cm wide by 203 cm long. This conversion matters more than shoppers expect — a growing share of USA buyers now cross-reference European or Asian furniture retailers, where centimeters are the default unit, so having both figures on hand avoids costly measuring mistakes.
King Size Bed Dimensions In Feet
When people search “king size bed dimensions in feet,” they’re usually asking about more than the mattress alone — they want to know how much total floor space the bed, frame, and headboard will occupy. The mattress itself stays at 6’4″ x 6’8″, but a bed frame typically adds:
- 1–3 inches on each side for the frame rails
- 4–6 inches at the head for a headboard
- 0–2 inches at the foot, depending on the frame style
A reasonable planning estimate for the full king beds footprint, frame included, is close to 6’6″ wide by 7 feet long — a number worth using instead of the bare mattress dimensions when you’re measuring your actual room.
King Size Bed Dimensions In Cm
In centimeters, that same full-frame footprint lands around 198 cm wide by 213 cm long, versus the mattress-only measurement of 193 cm x 203 cm. The gap between “mattress dimensions” and “bed dimensions” is small, but in a tight primary bedroom, those extra centimeters are exactly what separate a comfortable walkway from a cramped one.
Size
Beyond the king, U.S. mattress sizing follows a fairly predictable ladder. Here’s the full mattress size comparison chart:
Full Mattress Size Comparison Chart
| Size | Inches | Centimeters | Best For |
|---|---|---|---|
| Twin | 38″ x 75″ | 97 x 191 cm | Kids, single sleepers, small rooms |
| Twin XL | 38″ x 80″ | 97 x 203 cm | Taller solo sleepers, dorm rooms |
| Full | 54″ x 75″ | 137 x 191 cm | Solo sleepers wanting more width |
| Queen | 60″ x 80″ | 152 x 203 cm | Couples in average-sized rooms |
| King | 76″ x 80″ | 193 x 203 cm | Couples wanting maximum sleeping space |
| California King | 72″ x 84″ | 183 x 213 cm | Taller sleepers, narrow/long rooms |
A standard king mattress sits at the top of the width category, and only the California king mattress beats it on total length. Notice that a king and queen share the exact same 80-inch length — the extra 16 inches on a king is width, and width only.
King vs. California King Mattress: What’s the Difference
This is one of the most common points of confusion for shoppers, and it deserves a direct answer: a standard king and a California king mattress are not the same bed sized differently — they’re two different shapes built for two different problems.
- King (76″ x 80″): wider, better for couples who want maximum shared width, co-sleeping with kids or pets, or restless sleepers who move around at night
- California king (72″ x 84″): narrower but 4 inches longer, better for sleepers over 6’2″, or bedrooms that are long and narrow rather than wide
Important: bedding is not interchangeable between the two. Sheets, mattress protectors, and adjustable bases sized for a California king dimensions won’t fit a standard king, and vice versa. Always double-check the label before ordering accessories.
California Split King: The Alternative Worth Knowing
A California split king — and its standard-king equivalent, the split king — solves a problem a one-piece mattress can’t. Instead of a single mattress, it’s two separate Twin XL mattresses placed side by side, producing roughly the same overall footprint as a one-piece king.
This configuration solves three real problems:
- Different firmness preferences — one partner sleeps on a firm mattress, the other on plush, with zero compromise
- Independent adjustability — each side of a dual adjustable base raises, lowers, and reclines separately
- Reduced motion transfer — because the mattresses are physically separate, one partner shifting positions doesn’t disturb the other
A case study worth noting: shift workers and couples with mismatched sleep schedules are increasingly choosing split configurations specifically to avoid waking a partner who’s already asleep — a use case that’s grown alongside the rise of dual adjustable bases in the U.S. market over the past several years.
Style
A king size bed isn’t just a size — it’s a styling decision. Because king beds occupy a large visual footprint, they tend to anchor a room’s entire design rather than sit as one piece among many. Clean-lined platform frames, upholstered headboards, and neutral tones are especially popular choices, since they let the bed feel proportionate rather than overwhelming in a large bedroom space.
A few style notes worth considering:
- Platform frames suit modern and minimalist primary bedrooms
- Upholstered or sleigh-style headboards add a more traditional, hotel-like feel
- Storage frames (discussed more below) work well when floor space is limited despite the bed’s size
Because a king already commands significant visual space, designers often recommend keeping nightstands, dressers, and other furniture simpler in scale — letting the bed remain the focal point rather than competing with it.
Comfort
Comfort is where a king mattress makes its strongest case. With ~38 inches of personal width per sleeper, a king delivers noticeably more sleeping space than a queen’s roughly 30 inches per person. For couples, that extra width can mean the difference between waking up tangled together and waking up rested.
A king is especially well suited to:
- Couples who want a genuinely spacious couples bed without touching during the night
- Families who co-sleep with young children or pets who climb into bed
- Restless or light sleepers, where extra distance reduces the chance of being woken by a partner’s movement
- Larger primary bedrooms, where a queen mattress can visually look undersized
Comfort at king scale also depends on construction, not just size. Because two sleepers generate roughly twice the body heat and movement of one, materials that manage motion transfer and temperature regulation matter more on a king than on a smaller bed. Pocketed coils, breathable natural fibers, and open-cell foam structures all help two sleepers stay comfortable without disturbing each other.
Storage
Storage is one of the most overlooked factors when shopping for a king size bed, largely because the mattress’s size affects everything around it — including how much usable floor space is left for furniture.
What Room Size Do You Need for a King Bed
Before storage even comes into play, room size determines whether a king will feel spacious or cramped. The general guidance:
What Room Size Do You Need for a King Bed
| Room Size | Result With a King Bed |
|---|---|
| 10′ x 10′ (120″) | Roughly 22″ clearance per side — below comfortable walkway standards |
| 12′ x 10′ (144″) | Roughly 34″ clearance per side — workable minimum |
| 12′ x 12′ or larger | Comfortable clearance for nightstands, a dresser, and walkways |
A simple rule of thumb: keep at least 24 inches of walkway on each open side of the bed, and budget roughly 36 inches of clearance in front of any dresser so drawers can fully open.
Worked example: in a 12-foot-wide room (144 inches), a 76-inch-wide king leaves 68 inches of remaining space — split evenly, that’s 34 inches per side, comfortably above the 24-inch minimum. In a 10-foot room, that same math leaves only 22 inches per side, which is tight once a nightstand is added.
Storage-wise, king bed frames come in several configurations:
- Storage platform frames with drawers built into the base — useful in smaller bedroom space layouts where a dresser doesn’t fit
- Under-bed clearance frames — tall enough to slide bins or seasonal storage underneath
- Standard frames with a center support rail — required at king width to prevent sagging, regardless of storage style
Because a king mattress is heavier and wider than smaller sizes, the frame underneath needs a center support leg reaching the floor — without it, the extra width isn’t fully supported and sagging becomes a real risk over time.
Queen Size Bed Dimensions In Feet
For comparison, a queen mattress measures 5 feet wide by 6 feet 8 inches long (60″ x 80″). Notice the length is identical to a king — the two sizes only diverge in width, which is the single biggest factor in deciding between them for a couples bed.
How Wide Is A Queen Size Bed
A queen bed is 60 inches wide, giving each partner roughly 30 inches of personal width — a meaningful step down from the king’s 38 inches per sleeper. For solo sleepers or couples in more modest bedrooms, that difference rarely matters. For couples who move a lot at night, share the bed with pets, or simply want more breathing room, the extra 16 inches a king offers can make a noticeable nightly difference.
Queen vs. King — Width Per Sleeper
| Bed Size | Width | Width Per Sleeper |
|---|---|---|
| Queen | 60″ | ~30″ |
| King | 76″ | ~38″ |
Choosing between the two generally comes down to bedroom size: queens fit comfortably in bedrooms as small as 10′ x 10′, while kings are better suited to rooms 12′ x 10′ or larger.
Full Size Mattress Dimensions In Cm
Rounding out the size comparison, a full mattress measures 137 cm wide by 191 cm long (54″ x 75″). Full mattresses are typically better suited to solo sleepers wanting extra width than to couples — at just 137 cm wide, two adults would each have far less sleeping space than on a queen or king, making it a common choice for guest rooms, teenagers’ rooms, or single adults who want more room than a twin offers.
How to Choose the Right Mattress Size for Your Bedroom
With every size laid out, the decision usually comes down to a short checklist:
- Room dimensions — measure width and length before falling in love with any size
- Number of sleepers — solo sleepers rarely need more than a queen; couples benefit most from a king
- Kids or pets in the bed — a strong case for upgrading to a king
- Budget — king mattresses, frames, and bedding all cost more than queen equivalents
- Delivery access — doorways, hallways, and stairwells matter more with a one-piece king; a split king can solve tight-access delivery problems
Frequently Asked Questions
What are the exact king mattress dimensions? 76 inches wide by 80 inches long.
Is a king bed longer than a queen bed? No — same length, 16 inches wider.
What’s the difference between king and California king? King is wider; California king is longer.
What room size fits a king bed comfortably? At least 12 feet by 10 feet minimum.
Do two Twin XL mattresses equal a king? Yes — combined, they match king dimensions.
Is a king or queen better for couples? King, for maximum shared sleeping space.
Conclusion
To answer the original question directly: a king mattress measures 76 inches by 80 inches (6’4″ x 6’8″, or 193 x 203 cm) — the widest standard mattress size sold in the U.S. Whether you’re comparing it to a queen, weighing it against a California king, or considering a split king for adjustability, the decision ultimately comes down to your bedroom space, who’s sharing the bed, and how much room you want between you and your partner at night.
If your primary bedroom measures at least 12 by 10 feet and you’re sharing the bed nightly, a standard king mattress remains one of the most comfortable, spacious choices available — giving each sleeper roughly a twin bed’s worth of room, without compromising on length.
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Hi, I’m John Wick, the admin at Magazineaura.com. I make measurements simple and easy to understand, from bed sizes to everyday length conversions. Clear guides. Accurate dimensions. No confusion.
