Right-sized air, from the load to the last register.
Room BTUs, heat loss, airflow, duct sizes, SEER2 savings and ventilation rates, worked out before you buy or install. Every calculation runs in your browser.
Room BTU Calculator
Size a room air conditioner from floor area with the ENERGY STAR method, adjusted for sun, occupants, kitchens and tall ceilings.
Open → BTU/h · RHeat Loss Calculator
Estimate a home's design heating load from wall, window and ceiling areas, R-values, air leakage and design temperatures.
Open → CFMAirflow CFM Calculator
Work out the airflow in cubic feet per minute from a heat load and temperature difference, from room volume and air changes, or from tonnage.
Open → in. w.c./100 ftDuct Size Calculator
Size a round duct by friction rate or velocity, pick the standard size, and find rectangular ducts with the same capacity.
Open → SEER2 · kWhSEER2 Savings Calculator
Compare the yearly electricity use and cost of two air conditioners or heat pumps by SEER2 rating, with a simple payback.
Open → ASHRAE 62.2Ventilation Rate Calculator
Find the whole-house mechanical ventilation rate from ASHRAE 62.2, with air changes per hour and the fan size for intermittent running.
Open →These are estimates for planning and checking quotes. Whole-house equipment should be sized with a full Manual J calculation, and gas, electrical and refrigerant work must be done by licensed technicians.