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BTU Calculator

The calculator works out the result one room at a time. The boiler should be sufficient to supply your whole system.

Considerations for outdoor temperatures, external walls, windows, insulation and adjacent rooms, above, below and side by side are not taken into consideration with this calculator. Please be aware that a radiator with insufficient output may never raise the temperature to that required.

Room Type House Type Windows Type Room Sizes
Length (Metres)
Width (Metres)
Height (Metres)

BTU/hr Watts

This calculator is for guidance only.