HVAC & Refrigeration
Sensible Heat Load
Standard ASHRAE air-side sensible heat formula. Sensible (temperature) load only — this does not include latent (moisture/humidity) load, solar gain, occupancy or infiltration, which a full Manual J/Manual D style load calculation also accounts for.
Standard method — stated scope limits apply
Units
Enter airflow and temperature difference.
About This Calculation
The sensible heat load formula (Q=1.08×CFM×ΔT in imperial units, or the metric equivalent) is the fundamental relationship behind every HVAC cooling and heating load calculation — it’s literally how much heat a given airflow carries away (or delivers) for a given temperature change. A full building load calculation (Manual J, Manual D, or equivalent) layers solar gain, occupancy, infiltration and latent (humidity) load on top of this same core relationship.
Frequently Asked Questions
What does "sensible" heat mean, as opposed to "latent"?
Sensible heat changes temperature (what a thermometer reads); latent heat changes moisture content (humidity) without necessarily changing temperature — think of the difference between cooling dry air versus removing humidity from muggy air. This calculator covers sensible load only; a full comfort cooling load also needs the latent component, which requires psychrometric (humidity) data this tool doesn’t take as input.
Where does the 1.08 constant actually come from?
It’s derived directly from air’s physical properties: 60 minutes/hour × 0.075 lb/ft³ (standard air density) × 0.24 BTU/(lb·°F) (specific heat of air) = 1.08. It’s not an empirical fudge factor — it falls straight out of Q = mass flow × specific heat × ΔT.
Can I use this to size an air conditioner?
It gives you the sensible portion of the load, which is useful context, but sizing a real AC/chiller needs the TOTAL load (sensible + latent) plus safety margin — undersizing on sensible load alone risks an undersized system once real-world humidity load is added.
Why do the imperial and metric results not match exactly for an equivalent case?
Both use independently-rounded standard constants (1.08 vs 1.2, drawn from slightly rounded air density/specific heat figures common in each unit system’s own reference tables) — they agree to within about 1%, which is well inside the accuracy of a sensible-load estimate itself.