About the HVAC Calculator Toolbox
The HVAC Calculator Toolbox is a free collection of engineering calculators and reference tools built for HVAC professionals. It covers heating, cooling, ventilation, electrical sizing, piping, valve flow, and climate data — everything an engineer or technician needs to size equipment, verify designs, and troubleshoot systems in the field. Each calculator applies standard industry formulas from ASHRAE, NEC, and other recognized references so results are consistent with manufacturer ratings and code requirements. The site also includes ASHRAE weather station data for any location worldwide, an interactive psychrometric chart, and training videos. Whether you are selecting a rooftop unit, sizing ductwork, checking wire gauge, or looking up design day temperatures, these tools provide quick, reliable answers without manual table lookups or spreadsheet formulas.
Climate Tools
ASHRAE weather station data lookup and psychrometric analysis tools for HVAC design.
Cooling Calculators
Calculate cooling loads, SEER ratings, evaporative cooling, and DX coil performance for HVAC cooling systems.
Heating Calculators
Calculate BTU output, temperature rise, heat pump capacity, and gas heater sizing for HVAC heating systems.
Ventilation & Airflow
Calculate CFM requirements, duct sizing, fan energy index, and outdoor air loads for ventilation design.
Electrical Sizing
Calculate wire size, MCA, MOCP, and amperage per NEC standards for HVAC electrical systems.
Piping & Structural
Calculate duct sizing, friction loss, piping pressure drop, and pitched roof installations.
Valve & Flow Sizing
Calculate valve Kv/Cv coefficients, flow rates, pressure drops, and hydronic flow sizing.
Videos & Training
Professional development videos, equipment tutorials, and manufacturing facility tours.