UI - Set height of grid item equal to width

I am trying to achieve a basic inventory system based on a scrollable grid list.

I have a basic setup using a horizontal box with a few size box’s set to fill.

Now inside my grid panel i have defined the amount of columns desired (6) and set the scale to 1 which equally spreads them across the container as desired.

i just don’t know how to go about getting the items to be square. i tried setting the min aspect ratio option on the items size box to 1 which keeps the item a square but adds unwanted space between the items.

am i going to have to define everything manually in pixels?