Dividing by Zero Formula Solution

I am a real estate agent that uses an Excel spreadsheet to track real estate activity in our market. One of the measurements is called Months-Of-Inventory. This number tells me the number of months needed to sell existing inventory based on the average of previous 12 months sales. Formula is inventory divided by average of previous 12 months sales.

Here is the problem:

In one specific high-end price range, there is 19 active listings (homes for sale), but zero sales for the past 12 months. Cannot find solution to dividing a number by zero to arrive at a whole number that represents months of inventory.

Any ideas would be greatly appreciated!

I think you have more of a math problem than an excel problem.

Your formula is inventory/average of the previous 12 months sales. Let's abbreviate this to inv/s.

Is there a real estate publication that indicates an industry average for how long it takes to sell these very expensive homes? Let's say the industry average is 14. We will use ia for industry average. So we could change the formula so that the ia of 14 will be used if the last 12 months sales are zero.

So the formula would be IF(s = 0,ia,inv/s).

You would asterick the worksheet to say that the industry average is used if the last 12 months sales are 0.