How Wide Is a King Size Mattress? Exact Dimensions and FAQs
If you’re asking “How wide is a king size mattress?”, you’re usually trying to figure out whether it will fit your bedroom, your bed frame, or your lifestyle. This guide walks through exact king mattress widths, how they compare to other sizes, and what to consider before choosing one.
What Are the Exact Dimensions of a King Size Mattress?
In most of the United States, a standard king size mattress is 76 inches wide and 80 inches long.
- Width: 76 inches
- Length: 80 inches
This width is essentially the same as two twin mattresses placed side by side, which helps explain why it feels so spacious.
Why Does the Width of a King Mattress Matter?
Understanding how wide a king size mattress is helps with:
- Room layout: A king mattress can dominate a smaller room. Knowing the width helps you plan for walking space and furniture.
- Partner comfort: The extra width gives each person more personal space.
- Bedding and frames: Sheets, mattress protectors, and bed frames are sized based on exact dimensions.
A king’s width is especially helpful for couples, co-sleeping families, or anyone who likes to spread out.
How Wide Is a King Size Mattress Compared to Other Sizes?
Here’s a simple comparison of common mattress widths:
| Mattress Size | Width (inches) | Length (inches) |
|---|---|---|
| Twin | 38 | 75 |
| Full | 54 | 75 |
| Queen | 60 | 80 |
| King | 76 | 80 |
| California King | 72 | 84 |
A few key points:
- A king is 16 inches wider than a queen, but the same length.
- A California king is 4 inches narrower than a standard king, but 4 inches longer.
- If your main concern is width for shoulder room or sharing space, a standard king is usually the widest common option.
Are All King Size Mattresses the Same Width?
In most cases, yes for standard kings, but there are some variations you might come across:
Standard King (Eastern King)
- 76 inches wide x 80 inches long
- Most common “king” size in the U.S.
- Works with most king-size bedding and frames.
California King
- 72 inches wide x 84 inches long
- Not as wide as a standard king, but longer.
- Often chosen by taller sleepers who want extra foot room.
Split King
- Made from two separate mattresses, each typically:
- 38 inches wide x 80 inches long
- Placed side by side to create a combined width of about 76 inches.
- Helpful when partners prefer different mattress feels or want adjustable bases.
So if you’re comparing how wide is a king size mattress across these variations, remember: standard king and split king share the same total width; California king is slightly narrower.
How Much Space Do You Need for a King Size Mattress?
Knowing how wide a king size mattress is is only part of the picture; you also need to know if your room can handle it comfortably.
A common guideline is to leave at least 24–30 inches of open space around the sides and foot of the bed for easy movement. For many people, this means a king mattress works best in larger bedrooms.
Things to consider:
- Room width: Measure wall-to-wall and subtract 76 inches (king width) to see how much side clearance you’ll have.
- Furniture: Nightstands, dressers, and benches all take extra width.
- Doors and pathways: Make sure the mattress can be moved into the room through hallways and door frames.
Will King Size Bedding Always Fit a 76-Inch-Wide Mattress?
Most bedding labeled “king” is designed for a 76-inch-wide mattress, but there can be slight differences between brands.
For best results:
- Check the measured dimensions on packaging, not just the size label.
- Remember that fitted sheets must match both width and thickness; very thick mattresses may need “deep pocket” sheets.
- Comforters and duvets are often larger than the mattress on purpose, so they drape over the sides.
✔️ Quick Mattress Takeaways
Key points to understand about “How Wide Is a King Size Mattress”
- A standard king size mattress is 76 inches wide and 80 inches long.
- It is 16 inches wider than a queen, but the same length.
- California king mattresses are 72 inches wide and 84 inches long (narrower but longer).
- Split kings are made of two 38-inch-wide mattresses, forming the same total width as a standard king.
- King mattresses work best in larger bedrooms where you can leave comfortable walking space around the bed.
- Most “king” bedding is designed for a 76-inch width, but checking exact dimensions is helpful, especially for fitted sheets and mattress depth.
Understanding how wide a king size mattress is makes it easier to plan your space, choose matching bedding, and decide whether this size suits your sleeping arrangements now and in the future.
