Open the calculatorsOpen the calculatorsHVAC Calc Hub's calculators and guides are organized into nine topic areas. Here is what each one covers, so you can go straight to the tool that answers your question.
Open the calculators
The site groups 78 free tools and guides into nine topic areas, with 32 calculators among them. There are no trackers or pop-ups and no sign-up. Start from the HVAC Calc Hub homepage or jump straight to a topic below.
Sizing tools for air conditioners, furnaces, heat pumps, mini-splits, ducts, exhaust fans, ceiling fans and generators, plus unit conversions. Each one shows every step of the math, so you can check a contractor's numbers line by line.
Browse the HVAC calculators.
Step-by-step diagnosis for common cooling and heating faults, from an AC that will not blow cold to a furnace blowing cold air, ordered from the cheapest check to the one that needs a technician.
Browse the HVAC troubleshooting guides.
SEER2, EER2, HSPF2, AFUE, COP and CADR in plain terms, with what each rating means for your energy bills and how to compare two quotes fairly.
Browse the HVAC efficiency ratings explained.
Practical guides for window and portable units, return vents, filters, ceiling fans, humidifier and air purifier placement, and thermostat wiring.
Browse the HVAC installation and setup guides.
R-values, insulation targets by climate zone, MERV and HEPA filters, and air purification sized by CADR for the room it has to clean.
Browse the insulation and air quality guides.
What it really costs to run an air conditioner, heat pump, electric heater or dehumidifier at your own utility rates, and how gas and electric heating compare per delivered BTU.
Browse the HVAC energy cost calculators.
Refrigerant types from R-22 to R-454B, pressure-temperature charts, superheat and subcooling, and how technicians verify the charge.
Browse the refrigerant guides and PT charts.
Humidity, dew point, thermostat settings, heat pump temperature ranges and equipment lifespan: the numbers behind a home that feels right.
Browse the indoor climate guides.
Tank and tankless sizing, recirculation pumps, and the trade-offs between tank and tankless designs.
Browse the water heater sizing guides.
Sizing follows ACCA Manual J and S logic, psychrometrics follow ASHRAE Fundamentals and efficiency figures follow the DOE 2023 test procedures. Every calculator lists its equation and assumptions, and each tool says when a professional Manual J or on-site check is the right next step.
HVAC Calc Hub offers ac short cycling, ac tonnage calculator, ac vent temperature, afue rating explained, air changes per hour calculator, air purifier size calculator, average electricity usage by appliance, basement dehumidifier settings, bathroom fan cfm calculator, bathroom fan venting, btu conversion calculator, sacc vs ashrae btu, cadr rating explained, ceiling fan direction for summer and winter, ceiling fan downrod length calculator, ceiling fan size calculator, cfm calculator, duct size calculator, cold air return vents, condensation on ac vents, cop calculator, cost to run an air conditioner, cost to run an electric heater, cracked heat exchanger, dehumidifier freezing up, dehumidifier running cost calculator, dew point calculator, does ac remove humidity, how to drain a portable air conditioner, eer rating explained, furnace blowing cold air, furnace filter guide, furnace sizing calculator, gas vs electric heating, generator sizing calculator, heat pump efficiency vs temperature, heat pump running cost calculator, heat pump sizing calculator, heat pump temperature range, heating btu calculator, heating cost calculator, hepa filter guide, how long do ac units last, how long should it take to cool a house, how many btu air conditioner do i need, hspf rating explained, ideal ac temperature, ideal indoor humidity levels, insulation r-value chart, merv rating chart, mini-split sizing calculator, outside ac unit not running, can you recharge a window ac, hot water recirculation pumps, refrigerant pt charts, ac refrigerant types, seer rating explained, sones to decibels converter, superheat and subcooling calculator, tankless vs tank water heater, tankless water heater size calculator, thermostat not reaching set temperature, thermostat wiring explained, how to vent a portable ac without a window, water heater sizing calculator, what is r-value, where to place an air purifier, where to put a humidifier, window ac freezing up, how to install a window air conditioner, window ac leaking water inside, ac breaker keeps tripping, ac compressor replacement cost, ac drip pan overflowing, ac making noise, ac not blowing cold air, ac not removing humidity, ac refrigerant charge.