SCFM Calculator — Standard Cubic Feet per Minute

With this SCFM calculator, our aim is to support you in grasping the nuances of gas flow measurement under standard conditions. To understand more about this topic, please check out our gas density calculator and gas calculator.

In this article, we will talk about:

• What SCFM is;
• Its importance in evaluating and comparing gas flows in different conditions;
• How to calculate SCFM; and
• How to convert ACFM to SCFM calculation.

We will also use some practical examples to help you to understand the concepts and the SCFM calculation.

SCFM, or standard cubic feet per minute, is defined as the flow rate of gas that is corrected to a set of predefined standard conditions of temperature and pressure. It is a critical standard in the engineering world as it can facilitate precise design, comparison, and optimization of systems where gas flow is a key operational parameter.

Normally, these conditions are set at sea level atmosphere, which are 70 °F or 21.11 °C, and 14.7 psig, or 101.3 kPa. This allows for a consistent comparison of flow rates across different environments and systems, regardless of the actual operating conditions.

Hence, SCFM is useful when it comes to assessing and comparing the efficiency of pneumatic systems, HVAC units, etc. Engineers and technicians can adjust the flow rate to a common base line using the SCFM.

Now that you know what SCFM is, let's talk about ACFM. ACFM, or actual cubic feet per minute, is defined as the flow rate of gases in their real-world conditions.

Unlike SCFM, which normalizes the measurement to standard conditions, ACFM tells us about the volume of gas flowing per minute at the specific temperature and pressure conditions where the measurement is taken. This is important as ACFM can help to measure how the actual environmental conditions will impact its behavior.

Thus, ACFM is useful when it comes to ensuring that machinery receives the correct volume of air to operate effectively in a manufacturing process. Engineers can also use it to identify and predict maintenance schedules.

To understand how to convert ACFM to SCFM calculation, let's look together at the following example:

• ACFM: 100 cubic feet per minute
• Actual temperature: 50 °C
• Gauge pressure: 20 psig

You can convert SCFM from ACFM in three steps:

1. Identify the ACFM.

   The first step is to determine the actual cubic feet per minute (ACFM). In this instance, the ACFM is noted to be 100 cubic feet per minute.

2. Determine the actual temperature and pressure.

   Next, you need to identify the actual conditions under which the ACFM is measured. In our example, the actual temperature is 50 °C, and the gauge pressure is 20 psig. To understand more on this topic, please check out our pressure calculator.

3. Calculate the SCFM.

   With the conversion formula at hand, you can now calculate SCFM:

In this formula:

• The $\rm temperature$ should be in degrees Celsius.

• The $\rm pressure$ is the gauge pressure in psig (pounds per square inch at the gauge).

In our example, the SCFM is 214.95 cubic feet per minute.

Now that we know what SCFM is and how to calculate SCFM, let's dive deeper into understanding the topic. Humidity can significantly affect the density and behavior of gases, thereby influencing both the ACFM and the SCFM measurements.

When the humidity is high, the air contains less oxygen and nitrogen, affecting combustion processes, pneumatic systems, etc. Thus, when the humidity level is high, it can cause the ACFM to increase due to the decreased density of dry air.

You don't need to make any adjustments for the SCFM calculation as it assumes dry air. As for ACFM, to account for humidity, you need to adjust the discrepancy by incorporating specific humidity, which is the mass of water vapor per mass of dry air, into the conversion calculations.