HVAC Calculators
10 free professional-grade tools. HVAC load and sizing calculators for technicians
Heating & Cooling
BTU Calculator
Calculate the heating and cooling BTU requirements for a room based on square footage, insulation, climate zone, windows, and occupancy.
HVAC Load Calculator
Simplified Manual J HVAC load calculation for residential buildings. Estimates heating and cooling loads by size, climate, and occupancy.
AC Tonnage Calculator
Calculate AC tonnage for your home based on square footage, climate zone, insulation, and other factors.
Ductwork & Airflow
Duct Size Calculator
Calculate the required duct size for your HVAC system based on airflow (CFM), duct shape, and maximum velocity per ASHRAE guidelines.
Airflow CFM Calculator
Calculate the required airflow in CFM for any room based on volume and air changes per hour (ACH), or per ASHRAE 62.1 ventilation standards.
Cooling & Sizing
Gas Furnace Sizing Calculator
Size a gas furnace based on heating degree days, building envelope, and design temperatures. Follows simplified Manual J methodology.
Heat Pump Sizing Calculator
Size a heat pump based on climate zone, building envelope, and occupancy. Follows simplified Manual J methodology.