Online air conditioning tonnage calculators are available at LG.com, EasyCalculation.com and BlueStarIndia.com, as of 2015. Additional sources for tonnage and heat load calculators include Northernac.com and AlpineHomeAir.com.
EasyCalculation.com is a mathematics resource website that provides online calculation and learning tools including calculators, converters, tutorials and dictionaries. The website's air conditioning unit tonnage calculator determines the necessary tonnage by calculating a building's dimensions and details.
The Northernac.com free to use central air conditioning heat load calculator uses the square foot method which calculates a number of values to determine the necessary number of BTUs, nominal tons and recommended number of take-off duct registers. The calculated values include home dimensions, amount of insulation, and the number of windows and skylights.