This cannot be a rounded rectangle because those are not fully or "perfectly" rounded at the two ends. This is more like an elongated circle? A flat cylinder?

I searched a lot, but among all guides or pictures that identify and name different shapes, I couldn't get this particular shape. The closest I could get was a stretched ellipse.

There are only two processes to get this shape as far as I know: the first one is making a long rectangle and making its corner radius exactly half of the height. The second one is putting two circles a distance apart and adding a rectangle between those. So, are these something like "perfect rounded rectangles" or "rectangular circles"?

Stadium Shape

As a geometric figure.

A stadium is a geometric figure consisting of a rectangle with top and bottom lengths a whose ends are capped off with semicircles of radius r.

Sources mathworld.wolfram.com/Stadium.html / mentalfloss.com

Capsule Shape

Following @Rafael's answer, there are many results in Google as Capsule Shape

While perhaps not the "technical" term for it.. I see it often called a Pill Shape.

For me, it is a rounded rectangle just because the tool I would use is a rectangle and I would round it.

On a 3D model, I would use a sphere and move some vertexes.

But for non-graphic designers, I would call it a "Pill shape" Probably Penicillin pill shape.

Obround is another alternative. See this question on math.stackexchange or the wiktionary definition.

Two out of Wikipedia's five stadium references use obround instead.

A technical word for this kind of shape is Oblong.

See : https://www.vocabulary.com/dictionary/oblong

Ok, we need to clarify a few things.

1. While it's ok for the purposes of the question ("what's it called"), be aware that we are strictly in common usage territory here. There simply is no recognized terminology for this shape in Mathematics. Again, common usage satisfies the OP's question, but this addressing any notion that it's understood in mathematics.




2. You cannot use Wolfram as a source for this. Wolfram drills down it's citations to either Mathematica or their own Wolfram Language, neither of which represent the mathematics discipline as some kind of terminology force. Those are specific languages/products and need to be treated solely as that.




3. From a technical common usage position, in computer graphics and GUI design, both the decades of my primary experience, it is implemented and referred to (not rigidly defined) as a variant of a rounded rectangle, where the vertical legs have shortened to the point where the two quarter-circles have touched. Rounded rectangles in almost all cases, follow the circular curve on their corners.

Continuing on, an important further critique of the other answers:

4. To the answer from @Daniellio that shows two sources cited for it being called a stadium shape, **the second source refers directly to the first!* C'mon guys, you can't do that. It is one source, from Wolfram. And see point #1 above as to why you cannot use them.




5. To the answer calling it an oblong from @DavidHorizonef, No, it is not an oblong. An oblong is an elongated shape, and in curved situations, it is more akin to an oval, without parallel sides. Even the source he cites says this clearly.