Total Heat Calculator (4.5 × CFM × Δh)
Total heat uses enthalpy difference in BTU per pound of dry air, read from a psychrometric chart or calculated from wet-bulb readings.
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Formula
- Q (BTU/h) = 4.5 × CFM × Δh
Variables
- 4.5
- — 0.075 lb/ft³ × 60 min/h
- Δh
- — Enthalpy difference, BTU/lb dry air
Example calculation
1,200 CFM × 6.5 BTU/lb × 4.5 = 35,100 BTU/h ≈ 2.9 tons.
Practical HVAC use
Verify cooling capacity in the field from entering and leaving wet-bulb temperatures.
Common mistakes
- Using dry-bulb temperatures to look up enthalpy — use wet-bulb.
Related calculators
Sensible Heat
ProCalculate sensible heat in BTU/h and kW from airflow and temperature difference using Q = 1.08 × CFM × ΔT, with metric inputs.
Latent Heat
ProCalculate latent (moisture) heat load from airflow and humidity ratio difference in grains per pound: Q = 0.68 × CFM × Δgr.
CFM per Ton
ProCalculate airflow per ton of cooling and L/s per kW.
Educational tool. Results are estimates from the stated formulas; always confirm with manufacturer data and the code adopted in your jurisdiction. All calculators