My friends at humidordiscount.com have launched an useful service on their site. http://www.humidordiscount.com/humidor_calculator.php leads you to a page where you can feed in the measures of the humidor you are considering to purchase (or any other) and see how many cigars of different vitolas fits in. You can set default to your favourite cigar to quickly see the results.
The only improvement i suggested to them when reviewing the service was that you should be also able to feed in the quantities of the cigars you are going to store in the humidor, and the service gives you back the minimum measurements and suggestions from the product range. Now wouldn't that be convenient? If this suggestion flies and they introduce this service, i will most definitely utilize it when considering the choices for my next humidor.