Furnace Size (BTU) Calculator
Furnace output and input BTU from home size, climate, and AFUE.
Result
Furnace input rating (BTU/hr)
—
Heat output needed (BTU/hr)
—
Formula
Calculation logicWhat to check
- Conditioned floor area
- Furnace AFUE rating
Related calculators
Calculator
AC Size Calculator
Estimate central AC size in BTU/hr and tons from floor area and climate.
Open calculatorCalculator
Baseboard Heater Size Calculator
Watts and linear feet for electric baseboard.
Open calculatorCalculator
Boiler Size Calculator
Boiler gross output with piping and pickup allowance.
Open calculatorCalculator
Cooling BTU by Room Size
Room AC BTU from length, width, and ceiling height.
Open calculatorSaved calculations
Keep the assumptions with the result.
Save this calculation to return to the inputs, result, and report anytime.
Sign in or create an account to save this calculation.