ACH & CFM Calculator
Enter the space volume (in ft³), then pick whether you’re solving for CFM (given desired ACH) or ACH (given known CFM). Provide the needed input, and click “Calculate.”
1) CFM = (Volume × ACH) / 60
2) ACH = (CFM × 60) / Volume
Disclaimer: This is a simplified approach. Real HVAC design may consider infiltration, supply/return design, etc. for accurate calculations.
Integrated CFM and ACH Calculator
What is an ACH Calculator?
An Air Changes per Hour (ACH) Calculator is a tool used in HVAC (Heating, Ventilation, and Air Conditioning) design to determine how often the air in a given space is replaced per hour. ACH is a crucial metric in ventilation planning, air quality control, and energy efficiency in commercial and residential buildings.
This Integrated CFM and ACH Calculator allows users to compute either CFM (Cubic Feet per Minute) or ACH based on the inputs provided.
How It Works
This calculator supports two flexible modes of calculation:
1️⃣ Given Volume (ft³) & Desired ACH → Compute CFM
2️⃣ Given Volume (ft³) & Measured CFM → Compute ACH
This flexibility allows users to optimize airflow in various settings such as offices, hospitals, laboratories, clean rooms, and industrial spaces.
Formula Used in the Calculator
To Calculate CFM:
- CFM (Cubic Feet per Minute): The required airflow rate.
- ACH (Air Changes per Hour): The number of times air is completely replaced in the space per hour.
- Room Volume (ft³): The total space volume.
To Calculate ACH:
- ACH (Air Changes per Hour): Measures ventilation efficiency.
- CFM (Cubic Feet per Minute): Measured airflow through the HVAC system.
- Room Volume (ft³): Space volume for air circulation.
How to Use the CFM & ACH Calculator?
1️⃣ Mode 1: Calculate CFM (Airflow Rate)
- Input: Room volume (ft³) and desired ACH.
- Output: Required CFM to achieve the target ACH.
2️⃣ Mode 2: Calculate ACH (Air Changes per Hour)
- Input: Room volume (ft³) and measured CFM.
- Output: The actual ACH based on the given airflow.
Practical Applications
✅ Indoor Air Quality (IAQ): Ensures sufficient air exchange to remove contaminants and maintain health standards.
✅ HVAC System Sizing: Helps HVAC professionals determine airflow needs for various spaces.
✅ Hospital & Laboratory Ventilation: Ensures compliance with air quality and safety regulations.
✅ Energy Efficiency: Helps balance airflow needs with energy conservation.
Example Calculations
Example 1: Finding Required CFM
- A hospital isolation room has a volume of 2000 ft³, and regulations require 12 ACH.
- Using the formula:
- ✅ This room needs a ventilation system providing 400 CFM.
Example 2: Finding ACH from Measured CFM
- A classroom has a volume of 4000 ft³ and is receiving 500 CFM.
- Using the formula:
- ✅ This means the air in the classroom is being exchanged 7.5 times per hour.
Key Takeaways
🔹 CFM and ACH are essential for indoor air quality and ventilation efficiency.
🔹 This calculator provides a simple way to determine airflow needs or verify system performance.
🔹 Optimizing ventilation leads to improved comfort, safety, and energy savings.
Use the Integrated CFM & ACH Calculator to make data-driven decisions for HVAC system design, air quality management, and regulatory compliance.