BTU Calculator
Allbits Bathroom BTU Calculator
Estimate the heat output required for a warm, comfortable bathroom. Results are shown in watts and BTU per hour.
For lower water temperatures, the calculator increases the catalogue output you should look for.
Important: This calculator provides a practical estimate, not a formal room-by-room heat-loss design. Complex rooms, extensions, unusually large glazing, heat-pump systems or new heating installations should be assessed by an appropriately qualified heating professional. Compare products using the manufacturer’s stated output at the relevant ΔT rating.