Tray Visualizer
Wondering how many models fit on a tray? Pick a tray size, then add your bases below. By default the visualizer arranges them with a little breathing room to account for models that overhang their bases, but you can turn that off for a tighter fit. Treat the result as a good estimate rather than a guarantee; with careful arranging you may squeeze in a few more.
Add some bases to see how they fit on the tray.