Boiler Size Calculator
Estimate preliminary boiler heating capacity, input power, daily energy and operating cost from floor area, ceiling height and adjustable load factors.
Default project preview
87,285 BTU/h
Space-heating load
20.22 kW
Required input power
28.42 kW
Daily input energy
227.4 kWh
Daily energy cost
$27.29
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Base load uses area × entered load rate. Ceiling, insulation and climate factors adjust space heat. Hot-water allowance and reserve are added before dividing by efficiency.
FAQ
Boiler Size Calculator questions
Why can an oversized boiler be inefficient?+
Oversized boilers may cycle frequently and spend less time operating near efficient steady conditions.
Does this calculate radiator size?+
No. Emitters must deliver the room load at the intended water temperature.
Can domestic hot water require a larger boiler?+
Yes. Indirect tanks and combi systems can impose a different peak demand than space heating.