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Flex Top King vs. Split King: What’s the Difference?

When it comes to selecting the perfect bedding for your adjustable bed, understanding the difference between a flex top king and a split top king mattress is essential. Both options cater to specific needs and preferences, enhancing comfort and sleep quality. Let's dive into the details to help you choose the best mattress for your king bed setup.

Understanding the Basics

Twin Size: A twin mattress measures 38 inches wide by 75 inches long, making it a suitable option for children, teenagers, and single sleepers in smaller spaces.

Full Size: Also known as a double, a full-size mattress measures 54 inches wide by 75 inches long. It offers more width than a twin, making it ideal for single sleepers who want more room to move.

Queen Size: The queen size mattress is 60 inches wide by 80 inches long, providing ample space for couples while still fitting comfortably in most bedrooms.

King Mattress: A standard king mattress measures 76 inches wide by 80 inches long. It's ideal for couples who need ample space.

Split King: This is essentially two twin XL mattresses placed side by side, allowing each sleeper to adjust their side of the bed independently. This configuration is perfect for adjustable bases.

Split Cal King: Similar to the split king, but designed for a California king bed, the split california king is slightly longer and narrower than a standard king mattress.

A Wyoming King mattress measures 84 inches wide by 84 inches long, making it a perfect square. This size offers significantly more surface area compared to standard king and California king mattresses, making it ideal for families, couples who want more space, or even pet owners who share their bed with their furry friends.

Flex Top King

A flex top king mattress (also called a flex king, split top king or split top or split head mattress) features a split only at the top portion. This design allows the head section to be adjusted independently on each side, while the lower part remains connected.

Pros of a Flex Top King:

  • Individual Comfort: Allows each sleeper to adjust the head portion to their preferred angle without disturbing the other.
  • Unified Feel: The bottom part remains connected, providing a unified sleeping surface for a more traditional king bed feel.
  • Motion Transfer: Minimal motion transfer as the bed moves in unison from the mid-section down.


  • Limited Adjustability: Only the head portion can be adjusted independently, which might not be sufficient for those needing full body adjustments.
  • Bedding Compatibility: Requires specific bedding such as flex top flat sheets and deep pocket fitted sheets to accommodate the unique shape.

Split King

A split king is fully divided into two separate mattresses from top to bottom. This configuration allows both sides of the bed to be adjusted independently, making it ideal for adjustable bases.

Pros of a Split King:

  • Complete Customization: Both sleepers can fully customize their side of the bed, including head and foot adjustments.
  • Motion Isolation: Each side operates independently, reducing motion transfer and disturbance.
  • Versatility: Can be used as a single unified king bed or two separate mattresses, offering flexibility in use.


  • Separation: The gap between the two mattresses can be uncomfortable for couples who prefer to sleep close together.
  • Bedding Needs: Requires split king sheets and duvet covers, which may be harder to find compared to standard bedding sizes.

Bedding for Flex Top King and Split King

Finding the right bedding is crucial for both flex top king and split top king mattresses. Here's what you need to consider:

  • Flex Top King: Look for flex top fitted sheets and flat sheets designed to fit the unique shape. Ensure the duvet covers are compatible with the unified bottom portion.
  • Split King: Opt for split king bedding sets, which include two twin XL fitted sheets and a single king size flat sheet and duvet cover.

Choosing between a flex top king and a split king ultimately depends on your individual sleep needs and preferences. If you value head adjustability and a unified sleeping surface, a flex top king is a great option. However, if you need full adjustability and motion isolation, a split king might be the better choice.

In any case, investing in high-quality bedding, including deep pocket fitted sheets and appropriate duvet covers, will enhance your sleep experience. Remember, the best mattress for your adjustable bed is one that meets both your comfort and functionality requirements.

We at Overstock, offer both Split King and Flex Top King bed sheets. Shop here for Split King Sheet Sets. Shop here for Flex Top King Sheet Sets. Our sheets are designed to bring you the most comfort so you can experience the most restful sleep. 

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