How can I set up Reservation chart (inventory) for rooms in a small inn

How can I set up Reservation chart (inventory) for rooms in a small inn

Is this something done in a calendar?
or an excel file?

Or, is each night, in each room, it's own "product"? By that I mean a week's stay in one room would show the client purchasing 7 products (nights)?

Just not sure best way to track inventory.
It's best if its visual, similar to a calendar.  Is an excel file the answer?

Has anyone done something like this?