Sizing calculators
When the serial number says the equipment is near the end of its life, the next question is what size to replace it with. These calculators answer it and show the table or formula behind every number.
- BTU calculatorBTU for one room or a whole house
- Furnace size calculatorFurnace BTU from floor area and climate
- AC tonnage calculatorCentral AC size in tons from floor area
- Mini-split sizing calculatorBTU per zone for one to four rooms
- Water heater size calculatorTank size from your busiest hour of hot water use
- Tankless water heater size calculatorGPM, temperature rise, and BTU or kW
- Heat loss calculatorHeating load of a house, component by component
- CFM calculatorAirflow from tonnage, heat output or room volume
- Duct size calculatorRound and rectangular duct size from CFM
- Superheat and subcooling calculatorSuperheat and subcooling from pressure and line temperature
An estimate is a starting point. Heating and cooling equipment should be chosen from a room-by-room load calculation to ACCA Manual J. Replacing a unit with the same size as the old one repeats any mistake made the first time, and oversized equipment costs more, cycles on and off, and controls humidity poorly.
Not sure the old unit needs replacing?
Start with its age. The serial number decoder gives the month and year it was built, and the lifespan pages show how that compares with typical service life.