SITE TOOLS // RADIATOR SIZING ESTIMATOR
Radiator BTU Calculator
Work out roughly what size radiator a room needs – enter your measurements below.
ABOUT THIS CALCULATOR
Electric heating jobs live or die on sizing. Undersize the output and the room never warms up; oversize it and you have specified a load the customer pays for twice – once on the unit, once on every bill afterwards.
This calculator estimates the heat output a room needs in both BTU per hour and Watts, which is the figure that matters when you are specifying electric radiators or panel heaters and checking the circuit can carry them. Room type, insulation quality and the number of external walls all feed into the result, along with a 15% safety margin.
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Recommended Output
0 BTU/h
0 Watts, including a 15% safety margin
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This is a simplified estimate for guidance only, based on typical UK room heat loss rates. Glazing type, floor level, radiator position and exact insulation values all affect the real figure – for anything beyond a rough guide, get a proper heat loss calculation from a qualified installer.