An interesting and an easy view on calculating your potential market size for non-durable goods is to multiply all possible customers by all possible usage occasions. Sounds easy, right?
So, an example of how to calculate potential market size for pasta products in Italy.
Potential consumers: A country has a population of 60 million. We consider everyone to be potential product users except for those that have objective impediments not to use the product (e.g. kids below 6 months that just can not use pasta otherwise they die). It is imperative to include EVERY SINGLE person here, even someone who can not eat pasta due to gluten allergy (you can invent and sell him pasta without gluten), people with low income that can not afford to purchase pasta (as potentially you can invent such a low-priced product that they can buy it) etc. So, 97% of the target population will be considered as potential consumers.
Potential usage occasions: 2 times a day (he-he).
Maximum consumption quantity per usage occasion: 100 g
So - potential market size is 60M * 97% * 2 * 365 * 0.1kg = 4,248B tons of pasta per year.
Some watch-outs. Potential market by default can not be saturated, its potential can not reached. Well, technically it can be, but in reality I would guess this will never happen. AND its size can grow due to some changes in the market environment (e.g. significant product improvements, such as invention of special breakfast pasta which would potential usage occasions from 2 to 3, or pasta for kids below 6 months:)
So, next step is to determine where are the biggest gaps between current and potential market come from. Is your current market smaller because not all 97 % of people use pasta? (If so, why now what can you do to increase your penetration)? Or is it because they eat pasta less than 2 times per day (and what can you do to make different lunch, dinner and possibly even breakfast pasta)? Or does the biggest gap come from the fact that they use 97 g of pasta per occasion and not 100. These gaps exist due to product, price, knowledge/communication and availability problems. Only :) Now when you know the gap - what can you do to close it? Good luck!
And some trivia: did you know that EMRI scans are used in consumer research to detect human emotions towards some products / campaings? Another one: a necessity of the cork in a wine bottle is one of the biggest myths of wine business, a respected ritual (remember how sommelier pops-up the cork, explores, smells it and gives it to you so that you can smell it as well?) - that doesn't add any product quality benefits. But when you do it - you feel yourself a part of the special "wine lovers club" that know what to do with a used bottle cork..
(c) Prof. Troilo
SDA Bocconi