What Size Is a King Size Mattress? Dimensions, Variations, and FAQs
If you’re asking “What Size Is a King Size Mattress”, you’re likely trying to figure out if it will fit your bedroom, your bed frame, or your sleep needs. This guide explains standard king mattress dimensions, common variations, and what to consider before choosing one.
What Size Is a King Size Mattress in Inches and Centimeters?
In most places, when people say “king size mattress” they mean a standard king.
Standard King Mattress Size:
- 76 inches wide x 80 inches long
- Approx. 193 cm wide x 203 cm long
This makes a king wider than a queen (but the same length), giving couples more personal space side by side.
Are There Different Types of King Size Mattresses?
Yes. When you search “What Size Is a King Size Mattress”, you might see several variations. They are all “king” in name, but not the same size.
Common King Size Variations
| Mattress Type | Dimensions (W x L) | Notes |
|---|---|---|
| Standard King | 76" x 80" (193 x 203 cm) | Widely known as “Eastern King” |
| California King | 72" x 84" (183 x 213 cm) | Narrower but longer than a standard king |
| Split King | Two 38" x 80" (97 x 203 cm) | Same total size as a standard king |
Key point:
When you ask “What size is a king size mattress?”, the default answer is 76" x 80", unless “California king” or “split king” is specified.
Why Do King Size Mattress Dimensions Matter?
Knowing the exact king mattress size helps you:
- Check bedroom fit: Make sure you can still walk around your bed and place furniture comfortably.
- Choose the right bedding: Sheets, protectors, and toppers are size-specific. A king set will not properly fit a California king.
- Match your bed frame: A frame made for a queen or California king will not fit a standard king mattress.
- Plan for delivery and setup: King mattresses can be bulky. Measuring hallways, doorways, and stairs can prevent difficult setups.
For many couples, a king size mattress offers more personal sleeping space than a queen, which some people prefer for comfort when sharing a bed.
How Much Space Do I Need for a King Size Mattress?
A standard guideline is to allow extra floor space around the mattress for movement and furniture.
For a king mattress (76" x 80"), many people find it more comfortable in a room that is at least:
- Around 12 feet x 12 feet (approx. 3.7 m x 3.7 m), or larger.
This is not a strict rule, but it helps ensure there’s space for:
- Nightstands on both sides
- Room to walk at the foot of the bed
- Dressers, chairs, or other furniture
If your room is smaller, you might still fit a king, but the space could feel cramped, especially once a bed frame and headboard are added.
What Is the Difference Between a King and a California King?
This is one of the most common questions after “What Size Is a King Size Mattress”.
Standard King (76" x 80")
- Wider and shorter
- Often better for couples who want more side-to-side space
California King (72" x 84")
- Narrower and longer
- Often preferred by taller sleepers who need extra length
Both sizes provide a large sleeping surface, but bedding and frames are not interchangeable between them.
What About a Split King Size Mattress?
A split king uses two twin XL mattresses placed side by side:
- Each side: 38" x 80" (97 x 203 cm)
- Combined: 76" x 80", the same as a standard king
Common reasons people choose a split king include:
- Each sleeper can choose a different mattress feel (firmer or softer).
- Some adjustable bases are designed to move each side independently.
- It can be easier to move two smaller mattresses than one large one.
If you’re choosing a split king, you typically need split king sheets or separate twin XL fitted sheets.
✅ Quick Mattress Takeaways
Key points to understand about “What Size Is a King Size Mattress”
- Standard king mattress size: 76" wide x 80" long (about 193 x 203 cm).
- When you see the term “king” without qualifiers, it usually means this standard king.
- California king is 72" x 84"—narrower but longer than a standard king.
- Split king is two 38" x 80" mattresses placed together, equaling a standard king’s overall size.
- King mattresses fit best in a spacious bedroom, often around 12' x 12' or larger, depending on your furniture.
- Bedding, frames, and accessories must match the exact king type (standard king vs. California king vs. split king).
Understanding what size is a king size mattress—and how it compares to other king variations—makes it easier to measure your room, choose the right frame, and find bedding that fits correctly. With the dimensions in mind, you can decide whether a standard king, California king, or split king is the right match for your space and sleeping setup.
