Unity width and height of the gameobject

A GameObject doesn't have a width or a height but the information it contains could. In your case, you have a MeshRenderer and that conveniently has a bounds property which will return an...

axis-aligned bounding box fully enclosing the object in world space.

If you have a reference to the MeshRenderer on that object:

MeshRenderer renderer;

then getting the bounds is as easy as:

renderer.bounds;

and then you can observe its size property.

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Keep in mind this is the world space bounding information so all rotations and scalings will affect it. If you'd like the raw details of the mesh itself, you'll need a reference to the MeshFilter, look at its mesh property, and use the bounds property on that Mesh object.

There are 2 possible ways to do this. If your object has a renderer, you can use renderer.bounds.size, which will return a vector with the height and width (and depth, if it is in 3D).

You can also get the width and height from the colliders on a gameObject as well, by using collider.bounds.size. Try something like this:

public Vector3 size;
private MeshRenderer renderer;

private void Start() {
    renderer = GetComponent<MeshRenderer>();
    size = renderer.bounds.size;
}

Hope this helps!