CFM to Cmh Converter
Convert airflow between cubic feet per minute and cubic meters per hour. Enter values for instant results with step-by-step formulas.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
CMH = CFM x 1.699010796
Where CMH is cubic meters per hour and CFM is cubic feet per minute. The conversion factor 1.699010796 is derived from converting cubic feet to cubic meters (1 ft3 = 0.0283168 m3) and minutes to hours (x 60). To reverse the conversion, divide CMH by 1.699010796 to get CFM.
Worked Examples
Example 1: HVAC System Airflow Conversion
Problem:A residential air handler is rated at 1200 CFM. What is the equivalent airflow in CMH?
Solution:CMH = CFM x 1.699010796\nCMH = 1200 x 1.699010796\nCMH = 2038.81 cubic meters per hour\n\nAdditionally:\nLiters per second = 1200 x 0.471947 = 566.34 L/s
Result:1200 CFM = 2038.81 CMH
Example 2: Industrial Ventilation Requirement
Problem:A factory specification requires 5000 CMH of fresh air supply. What is this in CFM?
Solution:CFM = CMH / 1.699010796\nCFM = 5000 / 1.699010796\nCFM = 2942.88 cubic feet per minute\n\nThis would require approximately a 2.5 HP fan motor for typical duct systems.
Result:5000 CMH = 2942.88 CFM
Frequently Asked Questions
What is CFM and how is it used in HVAC systems?
CFM stands for Cubic Feet per Minute and is the standard unit of airflow measurement used primarily in the United States and other countries that follow imperial measurement systems. HVAC engineers use CFM to specify the volume of air that fans, blowers, and air handling units can move through ductwork every minute. A typical residential HVAC system moves between 400 and 2000 CFM depending on the size of the home and the capacity of the equipment. Understanding CFM ratings helps technicians properly size ductwork, select appropriate fan motors, and ensure adequate ventilation for indoor air quality requirements.
What is CMH and where is it commonly used?
CMH stands for Cubic Meters per Hour and is the metric equivalent of CFM used to measure volumetric airflow rates. This unit is standard across Europe, Asia, and most countries that use the metric system for engineering specifications. CMH is widely used in international HVAC standards, industrial ventilation design, and clean room specifications where metric measurements are required. When manufacturers produce equipment for global markets, they typically list airflow specifications in both CFM and CMH to accommodate different regional standards. CMH is also the preferred unit in ISO ventilation standards and European building codes for specifying minimum ventilation rates.
What is the exact conversion factor between CFM and CMH?
The exact conversion factor from CFM to CMH is 1.699010796, which means that one cubic foot per minute equals approximately 1.699 cubic meters per hour. This factor is derived from the relationship between cubic feet and cubic meters (1 cubic foot equals 0.0283168 cubic meters) combined with the time conversion between minutes and hours (60 minutes per hour). To convert CFM to CMH, multiply the CFM value by 1.699010796. To convert CMH back to CFM, divide the CMH value by 1.699010796 or equivalently multiply by 0.58857777. These conversion factors are precise enough for all engineering and HVAC design applications.
What are air changes per hour and how do they relate to CFM?
Air changes per hour (ACH) represents how many times the entire volume of air in a room is completely replaced in one hour. To calculate ACH from CFM, multiply the CFM by 60 to get cubic feet per hour, then divide by the room volume in cubic feet. For example, if a room is 2000 cubic feet and the ventilation system delivers 500 CFM, the ACH equals (500 times 60) divided by 2000, which gives 15 air changes per hour. Typical ACH requirements vary by space type: offices need 6-10 ACH, laboratories require 6-12 ACH, operating rooms demand 15-20 ACH, and clean rooms may need 20 to over 600 ACH depending on classification.
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy