Shouldn't 1gun turrets be smaller than 3 gun turrets?

[CenturionsofRome]

Exactly what it says. Currently 1 gun turrets have the same diameter as 3 gun turrets when they should actually be smaller.

[HusariuS]

Because 1 gun turrets are crewed by a stronk big boyz to load and traverse faster.

So they need bigger space.

[Illya von Einzbern]

In some cases this is true. For example 203mm single gun turrets would be smaller than double 203mm.
For large caliber guns 1 and 3 might not be that much of a difference. The turret ring will be more or less equally large due to plans for retrofit in case some treaties break or for future development.

The diameter will be the same but the shape and relative size will be smaller compared to triple gun configuration. After all there is no need to armor unnecessary space. Some turret designs comes up with the chance of adding more guns but those are rare and niche group.

[Bry7x7x7]

I mean, in some cases.

Like the Pensacola's found they needed to have a 2 gun turret for the 8 inch guns in the forward position under the 3 gun super firing one as the couldn't fit a barrette wide enough that close to the bow on this narrow of a hull.

Also it did so happen that the 11 inch 3 gun turrets on the "Pocket Battleships" of the Germans was about the right size to fit in a barrette for the 15 inch 2 gun turrets on the Bismark's which made a good stop gap measure for Scharnhorst class to be fitted with them in place of the 15 inchers they were meant to have.