Sleep Number Replacement Cover: How to Measure and Order the Right Size
Getting a Sleep Number® replacement cover that fits perfectly comes down to three things: the size of your mattress, the height of the foam shell, and the style of cover you have. Measure those correctly and your new cover will zip on like the original. Here is exactly how to do it.
The three measurements you need
Before you order, write down these three details. Most fit problems come from skipping one of them — usually the shell height.
- Mattress size — the length and width (Queen, King, Cal King, and so on).
- Shell height — the combined height of the parts that go inside the cover (the foam rails plus the comfort foam on top).
- Cover style — Smooth Top, Box Top, Euro Top, or Pillow Top.
Step 1: Measure length and width
Sleep Number beds use standard mattress dimensions, so once you know your size you know your length and width. Measure the foam shell itself (not the platform or frame) across the top, edge to edge. Use this chart to confirm:
| Size | Width x Length |
|---|---|
| Twin | 38" x 75" |
| Twin XL | 38" x 80" |
| Full | 54" x 75" |
| Queen | 60" x 80" |
| King | 76" x 80" |
| California King | 72" x 84" |
| Split King | two Twin XL halves (38" x 80" each) |
If your measurement does not match any of these exactly, do not worry — older and expanded sizes exist, and because our covers are made to order, we can match them. More on that below.
Step 2: Measure your shell height (the one people miss)
This is the measurement that matters most, and the one most often guessed wrong. The shell height is not the outside height of your old cover. It is the combined height of the components that sit inside the cover — the foam rails (which hold the air chambers) plus the comfort foam that lays on top. Those are the only pieces that move into your new shell. The quilted top stays part of the old cover, so do not measure it or add it in.
To measure it correctly:
- Unzip your current cover and set the quilted top aside.
- Stack the components the way they sit in the bed — foam rails on the bottom with the air chambers inside them, and the comfort foam on top.
- Measure the total height of that stack. That number is the shell height you order.
Measure the inside components (rails plus foam) — not the outside of the cover.
Example: if you have 6" foam rails and a 2" foam layer on top, that is 8" of components — so you order an 8" shell.
Changing your foam? Adjust the shell height to match
If you plan to change the thickness of your comfort foam, just add the difference to the shell height. The rails stay the same; only the foam on top changes. Using the example above:
- 6" rails + your current 2" foam = 8" shell
- 6" rails + a new 3" foam = 9" shell
- 6" rails + two 2" foam layers (4" total) = 10" shell
This is how you fine-tune the feel while you are at it — a thicker comfort layer for more cushioning, or a different foam on each side. You can browse replacement foam alongside your cover, or build your own comfort layer for newer models.
Step 3: Identify your cover style
Sleep Number shells come in a few distinct profiles. Look at the side of your current cover to identify yours:
- Smooth Top: a flat, uniform surface with no raised section. Common on newer smart-bed models.
- Box Top: a flat, even height all the way across, often with a dual-zipper design.
- Euro Top: a stepped profile with a raised section sewn flush to the edges.
- Pillow Top: an extra pillow layer sewn on top, giving the deepest, softest profile.
Matching the style matters as much as the size, because each one is built differently around the zipper and seams. If you are unsure which you have, our website has short videos that show each profile side by side.
Special cases: split-head, newer models, and discontinued sizes
A few setups need a little extra attention. FlexTop and split-head beds have a partial split at the head of the cover, so note whether yours splits and how far down. Newer smart-bed models often use a Smooth Top shell and may rebuild differently — if you have a newer model, you can even build your own comfort layer to match. And if your size was discontinued by the manufacturer, that is one of the most common reasons people come to us; a made-to-order cover can fit sizes that are no longer sold.
How to order the right cover
Once you have your size, shell height, and cover style, you can browse and order from our Sleep Number replacement covers, or see covers, foam, and rails together on the full repair parts collection. Every cover is made to order in the USA. If anything about your measurements is unclear, call us at 610-327-2322 before you order — we would much rather spend two minutes on the phone than have you receive the wrong size.
Frequently asked questions
What measurements do I need to order a Sleep Number replacement cover?
Three: the mattress size (length and width), the shell height measured from the base to the top of the shell, and the cover style (Smooth Top, Box Top, Euro Top, or Pillow Top).
How do I measure the shell height?
Unzip your current cover, set the quilted top aside, and measure the combined height of the parts that go inside: the foam rails (which hold the air chambers) plus the comfort foam on top. That total is the shell height you order — do not measure the outside of the old cover or include the quilted top. For example, 6" rails plus 2" of foam means an 8" shell. If you upgrade the foam thickness, add the difference (a 3" foam on 6" rails would be a 9" shell).
How do I tell a Box Top from a Euro Top or Pillow Top?
Look at the side profile. A Box Top is a flat, even height across. A Euro Top has a stepped, raised section sewn flush to the edges. A Pillow Top has a separate pillow layer sewn on top, creating the deepest profile.
Can I get a cover for a discontinued or unusual size?
Yes. Because our covers are made to order, we can match older, expanded, and discontinued sizes that the manufacturer no longer offers. Send us your measurements and we will confirm the fit.
The bottom line
A Sleep Number cover that fits perfectly is mostly about getting three measurements right: size, shell height, and style. Take your time with the shell height especially, match your cover profile, and you will order the right fit the first time. When you are ready, shop replacement covers or read our guide on whether it is worth repairing your Sleep Number bed.
