Expansion of the product depends on whether it is Foam Gun Grade or Hand-Held.  With Hand-Held foam, you can expect a growth rate of 150-200%, meaning that your joint/cavity needs only be filled with 30-40% for adequate coverage. Gun-Grade foam has the potential to expand by 50-100% when applied, requiring a minimum of a 50% fill for each gap or void.  Expansion rate is also dependent on temperature and humidity levels.