Total number of people who are potential customers * amount your product could sell for / number of realistic buyers * 10% == more realistic outlook. -- there

Total number of people who are potential customers * amount your product could sell for / number of realistic buyers * 10% == more realistic outlook. -- there are 7500 hospitals in the US which could buy my product for $100,000 dollars per hospital, but only 25% of them would actually be able to purchase it for various reasons of which I only have the ability to produce/call/sell to 10% of those in the first year == ((7500 x 100,000) x .25) x.10== ~$18,000,000 addressable market. Then I would get even more pessemistic and assume that you'll have an exceptionally long sales cycle getting out of the gate and that you'd only land say 10% of those customers in the first 12-18 months. while not hitting your stride fro say 36 months. Calc out your opex and this gives you an idea of the funds needed to support your runway.