Now I can measure down from the actual top of the frame to see exactly how much space I have available for drawers.
As you can see, we have 30 - 21/32" available to be split up between the drawers. Round numbers would be 30 - 5/8" for the drawers.
If I would split them up into 4 equal size drawers, ( I am not), I would divide the 30.656 - (30 - 21/32) by 4 and come up with a number of 7.664 inches for each drawer height, which will allow 1/4 inch spacing between drawers, including top and bottom spaces.
If I wanted to make it easier, I could use 7.5 inches for each drawer, which amounts to 30 inches.
The remaining space would amount to about 1.875 inches, or 1 - 7/8 inches for round numbers to be split 5 ways, which would allow or 3/8 inches spaces between drawers
This is talking about the drawer frames, and not the drawer fronts, which are typically a little larger than the drawer frames.
As you can see, it makes it very easy to split up the area for drawer height - which is assuming you followed what I am trying to say.
Hope that is a little clearer than mud.
