# How do you calculate CFM from static pressure?

## How do you calculate CFM from static pressure?

Fan Law 2 uses the following formula to calculate the relationship between airflow and static pressure:

- (cfm2 ÷ cfm1)2 x SP1 = SP2
- (cfm2 ÷ cfm1)2 x SP1 = SP2
- (1,200 ÷ 1,040)2 x .08 = SP2
- 1.152 x .08 = SP2
- 1.32 x .08 = SP2
- .11 in.

**How is airflow measured?**

An anemometer, a test instrument that measures air velocity is used to determine the average air speed in the duct. Then the average feet per minute is multiplied by the area of the duct in square feet to determine the airflow moving through the duct.

### How RPM is calculated?

How to Calculate Motor RPM. To calculate RPM for an AC induction motor, you multiply the frequency in Hertz (Hz) by 60 — for the number of seconds in a minute — by two for the negative and positive pulses in a cycle. You then divide by the number of poles the motor has: (Hz x 60 x 2) / number of poles = no-load RPM.

**How do you convert CFM to RPM?**

Define the terms in the general centrifugal fan formula and rearrange them to use the formula to solve for the higher air flow: CFM 1/CFM 2 = RPM 1/RPM 2 x (D1/D2)^3 (cubed).

## What is the equation for calculating CFM?

The formula for calculating how much CFM (cubic feet per minute) an engine requires is: CFM = Cubic Inches x RPM x Volumetric Efficiency ÷ 3456. Any ordinary stock engine will have a volumetric efficiency of about 80%.

**How do you calculate water column pressure?**

Determining Water Pressure. Use the formula pressure (P) = 0.43 x height of the water column in feet (h). We use the constant 0.43 (lb/in^2)/ft because this is the amount of pressure 1 foot of water places on a surface below it regardless of the volume of water.

### What is the pressure of a column of water?

One inch of water column is equal to a pressure of approximately 1/28 pound per square inch (psi). Stating this another way, a column water 28-inches high produces pressure that is equal to 1 psi.

**What is the measurement of water column?**

A water column is defined as a hypothetical cylinder of water extending from the surface to the bottom of the water body in consideration. Water columns are typically measured in inches and are used as non-SI units for pressure.