I was helping my partner figure out how many pebbles they needed to reach the maximum number of possible den slots at the moment, and I had a thought - why not make a tool for it? So I did, utilizing google sheets.
In order to use the tool, you must make your own copy of it by going to File > Make a copy. Once you have saved your own copy, follow the instructions below!
Using the DenCalc (slots) tab:
• Click the check boxes for the dens you currently have.
• Using the drop down menu, list how many slots you have in each den.
Using the DenCalc (slot cost) tab:
• Same as DenCalc (slots) tab, click the check boxes for the dens you currently have.
• Using the drop down menu, list how much your next den slot says it will cost when you click "Purchase Space" in that den. The tool will calculate your current slots for you from there.
Notes for use:
• You must check off dens you currently have in order, or the moonstone cost math will not be correct.
• You must check a box for a den for the slots in that den to count - you can check and uncheck boxes to project future expansion costs.
• It does not matter that you input your den slots per den in the order you acquired the dens in, just that the total number of dens are checked off in order.
Handy numbers (update to date as of March 3, '24)
• current maximum dens: 10
• current maximum slots per den: 50
• current maximum den slots: 500
• each den comes with 10 slots by default
• 1st additional slot costs 1000 pebbles; adds 1000 pebbles per additional slot up to the maximum of 40,000 pebbles for your 50th slot in that den
• 1st additional den costs 10 moonstones; adds 10 moonstones per additional den up to the max of 90 moonstones for your 10th den
See the References tab on the tool for costs of each specific den or den slot.
Skye 
