Return Air Calculator AC Size *PIck Your AC Size1.52.02.53.03.54.05.0CFM RequiredNumber of Returns *Enter the Number of Returns1234Return 1 Width (inches)Return 1 Height (inches)Return 1 CFMReturn 2 Width (inches)Return 2 Height (inches)Return 2 CFMReturn 3 Width (inches)Return 3 Height (inches)Return 3 CFMReturn 4 Width (inches)Return 4 Height (inches)Return 4 CFMRequired Air FlowTotal Return Area CFMCFM ComparisonA negative number means more return air is required.Check My Return Air