Latent Heat Load Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026What latent heat load measures
Latent heat load is the energy needed to add or remove moisture from the air, without changing its temperature. Cooling systems handle both sensible and latent load simultaneously, which is why a system can lower temperature quickly while indoor humidity still feels sticky if latent capacity is undersized.
Worked example
For 1000 CFM of airflow with a 30-grain moisture difference between return and supply air:
Q(latent) = 0.68 x 1000 x 30 = 20,400 BTU/hr
Grains of moisture per pound of dry air is a common humidity unit in HVAC psychrometrics - 7,000 grains equal one pound, and a psychrometric chart or app is typically used to find the grains value for a given temperature and relative humidity combination.
Adding this result to a calculated sensible heat load gives the total cooling load the system must handle.