Mesh not transforming to sphere blender

so im trying to make a sledgehammer in blender like this:image
but i cant get the edges to transform to a sphere like in the picture:

is there a way to fix this?

The mesh needs at least three separate vertices to perform this operation - ideally two edges. Try adding either some loopcuts (ctrl + r) or inset faces (i) to the selected face and it should work.

Otherwise you could bevel the edges of the face and then use proportional editing to move a series of inset faces outwards to create a smooth appearance.

Hope this helps.

Something else you could try, is bevels. It leads to poor topology most of the time, not quite sure. Go into edge select and select all the edges on the side and press Ctrl + B and move your mouse around til your happy with it and click.

Its called Blocking out, you dont block out Circles with cubes, just start with an sphere, you might need to union them or do some quick Booleans to get that shape of the hammer.

It is not impossible to make a cube into an sphere… but if you already have the sphere…

Anyway Ctrl R and expand the edges until you have a circle.

What are you looking to do is not Mesh > Transform > To sphere, you will end with bad topology.

What you are looking to use is LoopTools, search it, u will have to install the plugin on preferences.