What Is The Dimension Of a King Size Mattress? Exact Measurements & FAQs
If you’re asking “What Is The Dimension Of a King Size Mattress”, you’re usually trying to figure out whether it will fit your bedroom, bed frame, or bedding. This guide walks through standard king measurements, how they compare with other sizes, and what to double-check before you commit.
What Is The Dimension Of a King Size Mattress?
In most cases, when people ask “What Is The Dimension Of a King Size Mattress”, they are referring to the standard Eastern King.
Standard king size mattress dimensions:
- 76 inches wide x 80 inches long
- Approximately 193 cm x 203 cm
This makes a king mattress one of the widest common mattress sizes, giving each partner about the same width as a twin mattress.
Are There Different Types of King Size Mattresses?
Yes. While the standard king is the most common, there are several king variations that can cause confusion.
Standard King vs California King
Many people mix these up because “California King” sounds larger. In reality, it is just longer and narrower.
| Type | Width (in) | Length (in) | Best For |
|---|---|---|---|
| King (Standard) | 76 | 80 | Couples wanting maximum width |
| California King | 72 | 84 | Taller sleepers or narrow bedrooms |
A standard king offers more width, while a California king offers more length.
Other King Variations You Might See
Exact availability varies, but you may come across:
- Split King – Two separate mattresses, each 38" x 80", placed side by side to equal a standard king. Often used with adjustable bases or when partners prefer different firmness levels.
- Oversized Kings – Terms like “Wyoming King” or “Alaskan King” may appear, usually referring to mattresses larger than a standard king in both width and length. Their dimensions are not universal and are typically considered specialty sizes.
Why Do King Size Mattress Dimensions Matter?
Understanding what is the dimension of a king size mattress helps you avoid:
- A bed that overwhelms a small room
- A mattress that doesn’t match your bed frame
- Bedding that does not fit properly
A mattress that fits your space well can make it easier to move around the room, open doors and drawers, and arrange furniture comfortably.
How Much Space Do I Need for a King Mattress?
Beyond the mattress itself (76" x 80"), it helps to think about clearance around the bed.
Common practical tips:
- Aim for at least 24–30 inches of open space on the sides and at the foot of the bed for walking and everyday use.
- Don’t forget added length or width from a bed frame, headboard, or footboard, which can extend several inches beyond the mattress dimensions.
- Measure where doors, windows, and closets are so the bed does not block them.
A standard king often works best in larger bedrooms, where there is enough room for nightstands and walking paths on both sides.
Do All King Mattresses Have Exactly the Same Measurements?
Most standard king mattresses follow the 76" x 80" guideline, but there can be small variations:
- Some mattresses may measure slightly under or over due to materials, padding, or manufacturing tolerances.
- Mattresses with thick pillow tops or plush covers may appear larger even if the core measurement is similar.
- Over time, certain materials may settle or compress, which can subtly change how the edges measure.
Because of this, it’s common for fitted sheets and mattress protectors labeled “king” to allow a bit of extra room in both width and depth.
How Do King Dimensions Compare to Queen and Full?
If you’re upgrading, it helps to see what changes in size.
- Full (Double): 54" x 75"
- Queen: 60" x 80"
- King: 76" x 80"
Compared with a queen, a king mattress adds 16 inches of extra width while keeping the same length. Many couples notice that a king allows more personal space between sleepers.
What Should I Consider Before Choosing a King Size?
If you know what is the dimension of a king size mattress, the next step is deciding whether it fits your situation.
Key points to consider:
- Room size: Is there enough space for the bed plus nightstands, walking room, and storage?
- Doorways and hallways: Can a 76" x 80" mattress bend or move around corners and through doors in your home?
- Bed frame type: Platform beds, sleigh beds, or frames with thick side rails can use extra space.
- Bedding: You will need king-size sheets, blankets, and comforters to match the larger surface area.
- Sleep habits: Couples who move around at night or co-sleep with children often appreciate the extra width of a king.
✅ Quick Mattress Takeaways
Key points to understand about “What Is The Dimension Of a King Size Mattress”:
- Standard king size: 76" wide x 80" long (about 193 cm x 203 cm)
- California king: 72" x 84" – longer but narrower than a standard king
- Split king: Two 38" x 80" mattresses placed together to form a standard king size
- A king mattress typically fits best in larger bedrooms with room to walk around the bed
- Always measure your room, doorways, and existing bed frame before choosing a king
- Bedding and accessories should specifically match king dimensions for a proper fit
Understanding what is the dimension of a king size mattress makes it easier to plan your bedroom layout, select the right bedding, and decide whether this larger size is a practical match for your home and sleeping arrangements.
