Use the BTU calculator to quickly determine how much heat output your fireplace requires. It shows the appropriate BTU value, the propane or natural gas consumption and helps you to choose the ideal fireplace for any size of patio.
1 BTU calculator for fireplaces
Calculate the appropriate heat requirement (BTU/h) for your outdoor area – including kW equivalent, estimated fuel consumption (propane/natural gas) and operating costs.
Note: For outdoor situations, the entire room is not heated. The calculator uses heuristics (area x base BTU per m^2 x correction factors).
Assumptions: Propane ~ 46 000 BTU/kg, natural gas ~ 36 000 BTU/m^3. Efficiency according to input.
1 kW ~ 3412 BTU/h | 1 BTU ~ 0.000293 kWh
Calculation logic and assumptions
Basic formula: BTU = area (m^2) x 1200 BTU/m^2 x factors
- Wind protection: protected x0.8, partially x1.0, open x1.3
- Temperature: C 15 x1.00
- Seat spacing: 2.5 m x1.15
- Purpose: Heating x1.00, Ambience x0.70
Recommended range = +-15% around the target value, min. 15000 BTU/h, max. 200000 BTU/h.
Consumption formula: Consumption = BTU / (calorific value x efficiency). Propane ~ 46000 BTU/kg, natural gas ~ 36000 BTU/m^3.
Note: Practical guide value calculator for outdoor radiant heat, no heating load verification for indoor rooms.
2 Direct input: Consumption from existing BTU
Conversion: – kW | Assumptions: Propane ~ 46000 BTU/kg, natural gas ~ 36000 BTU/m^3.
