Cost Per Cfm Calculator - Calculator Academy (2024)

FAQs

How do I calculate how much CFM I need? ›

CFM Formula

Use the formula below to calculate CFM: CFM = (Room Volume in cubic feet) x (ACH) / 60.

1 ton of cooling is equal to 400 cubic feet of air per minute. 2 ton of cooling is 800 cfm and so on. So a 4 ton unit will have 1600 cubic feet of air passing through the system every minute.

AIRFLOW. Air quantities (cfm): 400 cfm per ton of cooling is needed for normal comfort applications, 500 cfm per ton of cooling for heat pump and high sensible heat applications, and 350 cfm per ton of cooling for high latent heat applications.

A good rule of thumb when calculating the cost of a compressed air leak is that one CFM* of air costs about $35 per shift annually (assuming an average energy cost of about $0.08/kW). If you run multiple shifts, multiply that number by 2 or 3; if your plant runs 24/7/365, multiply it by 4.2. How big is a 1 CFM leak?

ACH in simple terms is the number of times the air volume of the entire room needs to be changed every hour (Air change hour), and the air volume of the room is measured in cubic feet. So computed CFM will be = Air volume (i.e. Room's volume) x ACH (in hours) / 60.

1.3 cfm per sq ft

If you need to quickly determine how much cfm you need to deliver to a space, this is a great place to start. If the cooling load is relatively small, the system may require closer to 1 cfm/sq ft.

You can also calculate the air flow rate if you already know what the air velocity and pipe diameter are. With this information, you can use the following formula to determine the air flow rate: Q_air = u_air * π. D²/4.

For every AC ton, you need between 350 to 400 cubic feet of air per minute (CFM), i.e. a 2.5-ton AC needs 875 to 1,000 CFM, a 5-ton AC needs 1,750 to 2,000 CFM, etc. The specific airflow rate is determined by the size of the fan motor and what speed it runs at.

Therefore, a 3-ton residential cooling HVAC system should have 1,200 cfm of air across its evaporator coil. A 5-ton system should have have 2,000 cfm, a 6-ton system should have 2,400 cfm, and so on and son.

Most packaged air conditioning equipment is designed for, and rated at, 400 CFM per ton. Typically, a 7.5 ton unit will be selected with a drive package that causes it to deliver 3,000 CFM against whatever resistance the ductwork and grilles offer.

How many CFM do I need for a 12x12 room? ›

To adjust the CFM, you can change the speed of the blower or alter the ductwork size. Increasing the blower speed won't have much effect if a room's duct is too narrow. A 12' x 12' foot room is 144 square feet. You generally need at least 1 CFM per square foot, meaning that room's duct should have a 144 CFM capacity.

If you really need to know the true cost of compressed air, as a rule of thumb it is 10 times the cost of electricity. (Rule of thumb refers to a principle with broad application that is not intended to be strictly accurate or reliable for every situation.