Bathroom BTU Calculator
Estimate the heating output you need to keep your bathroom warm and comfortable.
Room Details
Enter your bathroom dimensions and characteristics
Recommended. Bathrooms often need extra heat due to extraction fans, tiled surfaces, and higher comfort expectations after a shower.
Recommended Output
For radiator or towel rail
Enter your room dimensions to see an estimate
What does BTU mean?
BTU (British Thermal Unit) measures heat output per hour. A higher BTU means more warmth.
When shopping for heated towel rails or radiators, match the BTU rating to your room's requirement.
Why volume (m³) not area (m²)?
Tile and flooring calculators use floor area (m²) because they measure surfaces.
Heating calculators use room volume (m³) because you're warming air — and higher ceilings mean more air to heat.
This calculator provides an estimate for planning purposes only. Final heating requirements should be confirmed by a qualified heating engineer who can assess your specific property and heating system.