What Size Is a King Mattress? Dimensions, Fit, and FAQs
If you’re asking “What Size Is a King Mattress”, you’re usually trying to figure out whether it will fit your bedroom, your bed frame, and your sleep needs. This guide walks through standard king mattress dimensions, how they compare to other sizes, and what to keep in mind before choosing one.
What size is a king mattress in inches and centimeters?
In most places, when people say “king mattress,” they mean a standard king (sometimes called an Eastern king).
A standard king mattress typically measures:
- 76 inches wide x 80 inches long
- 193 cm wide x 203 cm long (approximately)
This size offers the same length as a queen, but is wider, giving more personal space for each sleeper.
How does a king mattress compare to other sizes?
Understanding what size is a king mattress often means comparing it to other common mattress sizes.
Here’s a simple comparison:
| Size | Width x Length (inches) | Width x Length (cm, approx.) | Notes |
|---|---|---|---|
| Full | 54" x 75" | 137 x 191 | Tight for two adults |
| Queen | 60" x 80" | 152 x 203 | Common choice for couples |
| King | 76" x 80" | 193 x 203 | Wider than queen |
| Cal King | 72" x 84" | 183 x 213 | Longer, but slightly narrower |
Key takeaway:
A king mattress is 16 inches wider than a queen, but the same length. This extra width is one of the main reasons couples consider upgrading.
Are there different types of king mattress sizes?
When people search “What Size Is a King Mattress”, they sometimes confuse the standard king with other versions.
Standard King vs. California King
Standard King (Eastern King):
- 76" x 80" (193 x 203 cm)
- Wider, slightly shorter
- Often preferred by couples who want more side-to-side space
California King:
- 72" x 84" (183 x 213 cm)
- Narrower, but longer
- Can work better for taller sleepers or long, narrow rooms
Split King
A split king is still 76" x 80" overall, but it’s made of two separate 38" x 80" mattresses placed side by side.
This is popular when:
- Each sleeper prefers a different firmness
- Using an adjustable base with independently moving sides
Even though the construction is different, the overall size of a split king is the same as a standard king once it’s set up.
How much space do you need for a king mattress?
Knowing what size is a king mattress is only half the puzzle. You also need to know if it will comfortably fit in your room.
A common guideline is to leave enough open space for walking and furniture, not just to squeeze the mattress in.
✅ Helpful spacing tips:
- Leave at least 2 feet (about 60 cm) of open space on the sides and at the foot of the bed when possible.
- A king mattress often works best in rooms around 12' x 12' (3.7 m x 3.7 m) or larger.
- Measure for:
- Bed frame or headboard size (often larger than the mattress)
- Nightstands on both sides
- Doors, closets, or drawers that need room to open
Will king sheets and accessories fit all king mattresses?
Once you know what size is a king mattress, it’s easier to choose bedding that fits correctly.
- Standard King Sheets: Designed for 76" x 80" mattresses.
- California King Sheets: Sized for 72" x 84" mattresses and will not fit a standard king properly.
- Split King Sets: Usually include two twin XL fitted sheets plus one king-size flat sheet.
For best results, match your bedding to the exact type of king (standard, California, or split king) and consider extra-depth sheets if your mattress is particularly thick.
Who is a king mattress best suited for?
Understanding what size is a king mattress can help you decide if it matches your sleeping situation.
A king mattress is often a good fit for:
- Couples who want more individual space than a queen allows
- Co-sleeping with children or pets, where extra width is helpful
- Larger bedrooms, where a smaller bed might look undersized
On the other hand, in very small rooms, a king can dominate the space and leave limited room to move around furniture.
✔️ Quick Mattress Takeaways
Key points consumers should understand about “What Size Is a King Mattress”:
- Standard king size: About 76" x 80" (193 x 203 cm)
- Wider than a queen by 16 inches, but the same length
- California king is longer but narrower: 72" x 84" (183 x 213 cm)
- Split king equals a standard king in total size, made of two twin XL mattresses
- Works best in larger bedrooms, often around 12' x 12' or more
- Always match sheets and accessories to the exact type of king you own
With a clear understanding of what size is a king mattress, you can check your room measurements, consider your sleeping habits, and choose the configuration that fits both your space and your comfort needs.
