HVAC
Calculators.
Free precision tools — no signup.
AC BTU Calculator
Size air conditioning units by room dimensions and climate
HVAC Duct Sizing Calculator
Size round and rectangular HVAC ducts using ASHRAE equal friction or velocity method — velocity checks, pressure drop, and rectangular equivalents for any CFM
HVAC Load Calculator (Manual J)
Calculate residential heating and cooling loads using Manual J simplified method — BTU/hr by envelope, windows, infiltration, climate zone, with furnace and AC sizing
Furnace Sizing Calculator
Size a gas furnace or heat pump by climate zone, floor area, and insulation quality — output BTU/hr, AFUE efficiency, and 20-year fuel cost comparison
Heat Loss Calculator
Calculate heat loss or heat gain through any wall, ceiling, window, or floor assembly — U × A × ΔT with annual cost and insulation upgrade ROI
Ventilation Rate Calculator
Calculate required ventilation rates per ASHRAE 62.1 (commercial) and 62.2 (residential) — CFM, ACH, and zone-by-zone outdoor air requirements
Refrigerant Charge Calculator
Calculate total refrigerant charge for split systems based on capacity and line set length — with superheat/subcooling targets for R-410A, R-22, and R-32