Can someone help me calculate the height and width for each layer? I am guessing 15, 12, 9, and 6 for the squares, and 6 high, but then the bottom layer doesn't look tall enough to go with the other layers...

I am making a wedding cake like this for a friend in April for 125 guests. I'm not concerned with serving size, as I can do a dummie layer, or make a kitchen cake if I need to. I would like some assistance getting the visual part correct.

Thank you!

I think it's more like a 12 10 8 6. 4" high.

Ditto... 6, 8, 10, 12 all 4" high

I enlarged the picture on screen and got a tape measure (I tried using a calculator to get the ratios but couldn't get my brain to function)
I think they are:
6" x 4"
7" x 5"
9" x 5"
11" x 5"

or

6.5 x 4.25
7.5 x 5.5
9.5 x 5.5
12 x 5.5

The top tier is shorter than the others in any case.