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Quick answer
A king mattress is 76 by 80 inches per Amerisleep. A split king is two halves of 38 by 80 inches, which together are the same 76 by 80, and that half size is the twin XL size in Amerisleep’s chart. The three bases below are the Nestl 2nd Gen king (79 by 74 by 15 inches), the Best Choice Products split king (80 by 76 by 14.25 inches in two boxes, rated 750 pounds) and the Leggett and Platt S-Cape 2.0, whose page opened as a split California king (two bases, each 84 by 36 by 17 inches, 850 pound lift capacity). Amerisleep says memory foam and latex are the best mattress types for an adjustable base, and that a mattress up to 15 inches thick usually works.
Quick compare: the products in this guide
Sizes come from the Amazon listings as we read them; check the product page for the current details before you buy.
| Product | Listed details | Link |
|---|---|---|
| Nestl 2nd Gen King Adjustable Bed Frame with Massage and Wireless Remote | 79 x 74 x 15 in | See details on Amazon Affiliate link |
| Best Choice Products Ergonomic Split King Size Adjustable Bed Frame, Electric… | 80 x 76 x 14.25 in; 750 lb capacity | See details on Amazon Affiliate link |
| Adjustables by Leggett and Platt S-Cape 2.0 Adjustable Bed Base with… | 84 x 36 x 17 in each (split cal king page); 850 lb lift | See details on Amazon Affiliate link |
King versus split king
King (one base). One platform raises head and feet together. It is simpler and cheaper to move, and both sleepers get the same position.
Split king (two bases). Two halves, each 38 by 80 inches, each with its own remote position. Each sleeper chooses a position. Check with your mattress maker whether your mattress suits a split base.
Worked example: size, weight and height
This is our own arithmetic.
- Floor area. The Nestl base at 79 by 74 inches is 5,846 square inches, or 40.6 square feet; the mattress it carries is 42.2 square feet, so the base is 2 inches narrower than the mattress and the mattress overhangs by 1 inch on each side. The Best Choice split king at 80 by 76 inches is 6,080 square inches, 42.2 square feet, the same as the mattress.
- Height. With a 12 inch mattress (an example), the Nestl base puts the top of the mattress at 15 plus 12, which is 27 inches from the floor with the base flat; the Best Choice base puts it at 26.25 inches.
- Load. Take an 80 pound mattress and two adults of 350 pounds together, which is 430 pounds (assumptions). Against the Best Choice rating of 750 pounds, that is 57 percent. The listing does not say whether the rating includes the mattress.
- Moving. The Best Choice base ships in two separate boxes, which for a split king means two halves; the Nestl listing text we read does not say how it ships.
What the listings say
Nestl 2nd Gen King Adjustable Bed Frame with Massage and Wireless Remote (ASIN B0DCX5WTKX). The table gives alloy steel, a product size of 79 by 74 by 15 inches and black. The bullets give head and foot elevation, one-touch zero gravity, anti-snore, TV, lounge and flat presets, head and foot massage in three modes with 10 to 30 minute timers, under-bed LED lighting, USB ports and a zero clearance design that the listing says works with many platform frames. The text we read states no weight or rating. Best for: a single king base with a full set of presets. Watch out: no rating in what we read, and zero clearance means it must fit inside your frame.
Best Choice Products Ergonomic Split King Size Adjustable Bed Frame, Electric Base with Wireless Remote (ASIN B08BJCW16S). The table gives 80 by 76 by 14.25 inches, fabric and metal, two packs and grey or black. The bullets give TV, head-tilt and zero gravity presets with room for custom positions, a remote with massage and a flashlight, separate head and foot incline, a bedside USB port, a side pocket and under-bed night lights, and say the base is compatible with various mattresses. The page text states a weight capacity of 750 pounds and items in two separate boxes. Best for: two sleepers who want independent halves. Watch out: you assemble two bases, and the rating is the seller’s.
Leggett and Platt S-Cape 2.0 Adjustable Bed Base with Wallhugger Technology and Full Body Massage (ASIN B06XSTGMX5). The page opened as a split California king, with two bases of 84 by 36 by 17 inches each, steel and charcoal gray upholstery. The table lists maximum capacities of 700 and 850 pounds for different versions, and the bullets give an 850 pound lift capacity motor, a 4 inch profile, 6 to 10 inch adjustable legs, a back-lit wireless remote with zero gravity and two programmable positions, under-bed lighting, dual massage, a snore button, a hook system that removes the need for a mattress retainer bar and warranties of 1, 3 and 25 years. Best for: a base whose listing states legs, warranty and lift capacity. Watch out: the page opens on a different size from king, so choose king in the selector and check its dimensions.
How the three compare
| Listing | Type | Size | Rating stated | Warranty stated |
|---|---|---|---|---|
| Nestl 2nd Gen | One king base | 79 × 74 × 15 in | Not in the text we read | Not in the text we read |
| Best Choice Products | Split king, two boxes | 80 × 76 × 14.25 in | 750 lb | Not in the text we read |
| Leggett and Platt S-Cape 2.0 | Split (page opened as cal king) | 84 × 36 × 17 in each | 700 to 850 lb | 1, 3 and 25 years |
Mattress fit for a king base
Amerisleep’s guide says memory foam is a top pick because it bends and keeps its shape, latex is another excellent option, hybrids may work depending on construction and a traditional innerspring is generally not suitable. It also says mattresses up to 15 inches thick usually work best and that a mattress should be at least 8 inches thick to avoid sliding. For a split king, a single king mattress will not move the way two half mattresses do, and the maker’s guidance may require split mattresses.
How to choose
Choose single or split first. Split is better if the two sleepers want different positions; single is simpler.
Match the mattress. Check the maker’s words on adjustable bases.
Check the frame. A zero clearance base sits inside a platform frame; ask whether yours is one.
Plan the delivery. A king base is heavy and arrives in two or more boxes in some cases; ask for the weight.
Power, placement and questions to ask
A motorized base needs a socket within reach, and the three listings we read do not give a cord length, so measure from the head of the bed to the nearest outlet and ask the seller. The Leggett and Platt listing names a wall-hugging design; the other two listings do not describe how close to a wall the base can sit, which matters if your bed stands tight against the headboard wall.
Questions worth sending before you order: what is the weight of the heaviest carton, does the rating include the mattress, does the base work with a power outage (some have a battery backup, and the listings we read do not say) and what is the warranty on the motor. A reply in writing is worth keeping with the order.
Mistakes to avoid
Buying a king base for a split mattress, or the reverse. The two are not interchangeable.
Using an innerspring mattress. Amerisleep says it is generally not suitable.
Ignoring power. A base needs a socket within reach of its cord.
Trusting the page’s default size. The S-Cape page opened as a split cal king.
When a different base is better
For queen and twin bases, see adjustable mattress base. For a plain king platform frame, see king platform bedframe. For king mattress pairing, see king mattress with frame.
Frequently asked questions
What is a split king adjustable base?
Two bases of 38 by 80 inches that together fit a 76 by 80 inch king mattress and move independently.
Which mattress works on an adjustable base?
Memory foam and latex are top picks per Amerisleep; hybrids depend on construction; innerspring is generally not suitable.
How thick can the mattress be?
Up to 15 inches usually works best, and at least 8 inches to avoid sliding.
How heavy is a king base?
The listings we read give no weight in the table. Ask the seller.
Does a base need a frame?
Some bases stand on legs; the Nestl is a zero clearance design that fits inside many platform frames.
Are adjustable bases quiet?
The listings say quiet motors; we have not tested them.
Products worth checking
We have not tested these products. Sizes and features come from the Amazon listings as we read them; where a listing does not say, we say so.
Nestl 2nd Gen King Adjustable Bed Frame with Massage and Wireless Remote
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
Best Choice Products Ergonomic Split King Size Adjustable Bed Frame, Electric Base
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
Adjustables by Leggett and Platt S-Cape 2.0 Adjustable Bed Base with Wallhugger Technology
- Keep in mind: we have not tested it, and the listing may show more than one size or finish, so pick the variant that matches your numbers.
Sources checked
- Amerisleep: Do You Need a Special Mattress for an Adjustable Bed?
- Amerisleep: mattress sizes and dimensions chart
Specifications come from the Amazon listings as we read them for this guide. Product details and availability can change, so confirm on the product page before you buy.
