HVAC & Climate Calculators

Tools for HVAC technicians, installers and building designers. Load estimates are clearly labeled rule-of-thumb methods; duct sizing uses the standard equal-friction equation for round galvanized duct.

• BTU CalculatorEstimate the cooling load in BTU/h for any room from floor area, climate, insulation, sun exposure, occupants and appliances. Includes tonnage and CFM guidance.
• Heating Load CalculatorEstimate heating load in BTU/h and kW from floor area, design temperature difference and insulation quality. Includes ventilation adjustment guidance.
• Duct Size CalculatorSize round HVAC ducts from airflow (CFM) and friction rate using the ASHRAE equal-friction method. Gives exact diameter, nominal size, velocity and metric equivalent.
• Airflow / ACH CalculatorConvert between airflow (CFM, L/s, m³/h) and air changes per hour for any room volume. Includes typical ACH targets for bedrooms, bathrooms and kitchens.
• SEER / EER / COP ConverterConvert SEER to EER, COP and kW per ton of cooling. Understand what efficiency ratings mean for real electricity costs and how the ratings differ.
• Dew Point CalculatorCalculate dew point and approximate wet-bulb from temperature and humidity, with comfort interpretation. Magnus formula, °C and °F.
• Duct Velocity CalculatorCheck air velocity in a known duct: enter CFM and diameter to get fpm, m/s, duct area and the estimated friction rate. Includes noise guidance.
• AC Running Cost CalculatorCalculate air conditioning running cost from tonnage, SEER, runtime and electricity rate. Monthly and seasonal figures for upgrade comparisons.
• Heat Index CalculatorCalculate the heat index (feels-like temperature) from air temperature and humidity using the official NWS Rothfusz regression, with risk levels.
• Wind Chill CalculatorCalculate wind chill from temperature and wind speed using the official NWS formula, with frostbite time estimates for exposed skin.
• Degree-Day Heating CalculatorEstimate heating fuel use and cost from degree-days and house heat-loss coefficient. Supports gas, oil, propane and electric heating.
• Sensible Heat & Airflow CalculatorSolve the sensible heat equation: find airflow from BTU/h and ΔT, or BTU delivered from known airflow. Metric equivalent included.
• Fan Laws CalculatorApply the fan affinity laws: how airflow, static pressure and power change with fan speed. The cubic power law explains VFD energy savings.