BTU vs CFM: Sensible Heat, Airflow Velocity & Cooling Capacity
BTU (British Thermal Unit) measures total thermal energy transfer capacity per unit time, whereas CFM (Cubic Feet per Minute) measures the volumetric rate of air movement. In HVAC design, the sensible heat formula bridges airflow velocity and heating/cooling output.
Technical Comparison & Conversion Matrix
| Parameter | BTU / BTU/hr | CFM (Cubic Feet / Min) |
|---|---|---|
| Physical Dimension | Power / Thermal Transfer Rate | Volumetric Flow Rate |
| SI Equivalent | 1 BTU/hr = 0.293071 W | 1 CFM = 0.0004719 m^3/s (1.699 m^3/h) |
| HVAC Role | Equipment sizing (tonnage: 12,000 BTU/hr/ton) | Duct design and air distribution velocity |
| Sensible Heat Link | Q = 1.08 * CFM * Delta_T | CFM = Q / (1.08 * Delta_T) |
| Typical Rule of Thumb | 20 to 30 BTU/hr per sq ft conditioned | 400 CFM per nominal cooling ton |
Live Calculator: BTU to CFM Airflow Calculator
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Computed Output
Interactive Online Calculators
Instantly compute exact values using our deterministic edge calculation tools:
BTU to CFM Airflow Calculator
Convert sensible heating and cooling BTU/hr to required CFM airflow and tonnage for HVAC design.
CFM to BTU/hr Capacity Calculator
Convert airflow CFM and temperature split to sensible thermal BTU/hr output for HVAC equipment.
Residential & Commercial Heat Load (Manual J) Tonnage Calculator
Estimate residential cooling and heating heat loss/gain in BTU/hr and required HVAC air conditioning tonnage.
Frequently Asked Questions
How do you calculate CFM required from a known BTU cooling load?
Divide the sensible BTU/hr load by (1.08 * temperature split across evaporator coil). At standard sea-level air density with a 20°F split, 12,000 BTU/hr requires approximately 555 CFM of sensible air circulation.
Why is the constant 1.08 used in the sensible heat formula?
1.08 is the product of standard sea-level air density (0.075 lb/cu ft), specific heat capacity of dry air (0.24 BTU/lb-°F), and 60 minutes per hour: 0.075 * 0.24 * 60 = 1.08.