New: see our HVAC Sizing Calculator hub for all tools plus a complete how-to-size guide.
Calculators
Free HVAC calculators for homeowners, DIYers, and contractors. Size your system right the first time and save thousands on equipment and energy bills.
Load & Size Calculators
BTU Calculator
Calculate BTU heating and cooling requirements for any room based on size, climate, and insulation.
Use Calculator →AC Unit Size Calculator
Find the right central AC tonnage for your home across all climate zones.
Use Calculator →Furnace Size Calculator
Calculate the BTU output needed for your furnace based on square footage and heating zone.
Use Calculator →Mini Split Size Calculator
Size a ductless mini-split for any room, garage, addition, or sunroom application.
Use Calculator →Heat Pump Size Calculator
Calculate heat pump tonnage and compare savings vs. your current gas or electric heating system.
Use Calculator →Airflow & Ductwork
CFM Calculator
Calculate required airflow (CFM) for any room based on volume and air changes per hour.
Use Calculator →Duct Size Calculator
Size round, rectangular, and flexible ducts for any airflow requirement. Includes velocity table.
Use Calculator →Ventilation Calculator
Calculate fresh air ventilation requirements per ASHRAE 62.1/62.2 for any space type.
Use Calculator →Energy & Refrigerant
HVAC Energy Cost Calculator
Estimate annual cooling costs and savings from upgrading to a higher SEER-rated system.
Use Calculator →Refrigerant Charge Calculator
Estimate additional refrigerant needed based on line set length for R-410A, R-32, and R-454B systems.
Use Calculator →🌡️ Recommended HVAC Equipment
A programmable thermostat can cut your heating and cooling costs by 10-15%.
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