View Products

ROOM BY ROOM

BTU Calculator

A useful starting point for choosing your radiator heat output. Tell us about your room to see an estimated range.

Your room

Sheltered: protected by nearby buildings. Exposed: open or windy surroundings.

Room dimensions

Use internal dimensions. Length and width: 0.5–20 m. Height: 1.5–4 m (or the equivalent in feet).

What does BTU mean?

A British Thermal Unit measures heat energy. Radiator outputs use BTU per hour (BTU/hr) or Watts to describe the rate of heat delivery. Correct sizing helps a room reach its intended temperature without relying on an undersized radiator.

Comparing radiator outputs

ΔT50 means the average water temperature is 50°C above the room temperature. A common reference is 75°C flow, 65°C return and a 20°C room. It does not mean a 50°C flow temperature.

The room heat requirement stays the same at lower water temperatures, but a radiator delivers less heat. For heat pumps or other low-temperature systems, use manufacturer output data at your actual temperatures and ask your installer to confirm the size.