Samsung Galaxy S21 Plus Case vs S21 Ultra Case: What’s the Difference?

The Galaxy S21+ and Galaxy S21 Ultra look similar at a glance, but their bodies are built to different dimensions. A case designed for one won’t fit the other correctly, and forcing it on can leave edges exposed or block the camera.

Do S21 Plus and S21 Ultra Cases Have the Same Size?

No. The two phones have different body dimensions, so their cases are model-specific and not interchangeable. The S21 Ultra is both taller and thicker than the S21+, while the two share an identical width of 75.6 mm.

Samsung’s published specs for the two models spell out the difference clearly:

That extra thickness comes largely from the larger camera housing and bigger battery, which also explains the 27 g weight gap.

What Happens If You Use the Wrong Case?

Neither direction fits well, and each mismatch fails differently.

• S21+ case on an S21 Ultra: The case is too short and too thin. It won’t fully cover the top and bottom edges, and the camera cutout won’t line up with the Ultra’s larger camera module. Buttons may also sit slightly off their switches.
• S21 Ultra case on an S21+: The case is too tall and too thick. The phone will shift inside it, leaving the upper and lower edges exposed to drops. The camera cutout will be oversized, and the extra bulk makes the grip feel wrong.

In both situations, the case fails at its one job—protecting the phone. A loose fit also lets dust and debris work their way between the case and the body, which can scratch the frame over time.

If you’re looking at cases for the smaller of the two phones, our tested roundup of the best case options for the S21 Plus narrows down the models that actually fit.

Why Same Width Doesn’t Mean Same Fit

Both phones measure 75.6 mm across, which makes it easy to assume a case will stretch between them. That assumption fails because a case grips a phone in three dimensions, not one. The S21 Ultra’s extra 3.6 mm of height means a case molded for the S21+ stops short of the phone’s top and bottom edges. Its extra 1.1 mm of thickness means the side rails sit tighter than they should, pressing against the volume rocker and power button.

Screen size is an even weaker guide. The bezels and body proportions differ, so the cases don’t.

Which Galaxy S21 Phones Share a Case?

None of them, within the S21 family. The standard Galaxy S21 5G, the S21 FE 5G, the S21+, and the S21 Ultra each have their own body dimensions and their own case fit.

• The S21+ and S21 Ultra are the two biggest, at the dimensions listed above.

Always check the model name printed on the case listing before buying. A listing that says “Galaxy S21” without a “Plus,” “Ultra,” or “FE” suffix almost always refers to the standard model only.