Our simple and easy to use calculator helps you determine the estimated amount of Helium per Balloon and the Number of Helium Tanks you might need. In other words once the gas inside the tank reaches atmospheric pressure it will no longer be able to fill balloons. Pin On Let S Party How many balloons are in a 10 pound nitrous tank. . 1 800 538-5800 M-F Why we built this calculator just for you yes you. With the ability to fill up to 350 balloons per tank which they sell for 5 and 10 they can bank more than 300000 per festival minus expenses. Keep in mind that an exhausted helium tank is not empty. Yes two birds one calculator. For each size tank we tell you how many balloons you can fill for each size of balloon from 9-inch latex to 18-inch foilmylar balloons. So with that math assuming 20g per balloon there would be 454 balloons in a 20 lb tank. A k tank holds 194 cf of helium and will fill. Also provided