This app is design to calculate gas consumption on a meter. It can be used to check for inefficient appliances or total home or business consumption. It is design to work on pressure ranges: 7" water column, 2 psig, 5 psig, or 10 psig systems and meter index size 1/2 cu ft, 1 cu ft, 2 cu ft and 5 cu ft. Simply select your pressure then select your index measurement size and then enter the number of seconds to took to make 1 revolution then press calculate and it tell you how many BTU per hour are being consumed. You can now use this information to check against the rating plate on your appliance being tested to see if it under/over fired. Poorly running appliances can cost your hundreds of dollars and not to mention can be unsafe to operate.