Too large a radiator and you will waste your money buying a radiator you don’t need and losing wall space you could utilise in other ways.
Oversized radiators can also waste energy by burning more gas or electricity.

Building characteristics matter as every room is different. Size / insulation quality / window area and even orientation to the sun all affect how much heat a room loses. Our handy calculator allows you to get an insight into what radiator will suit your room best.
Different rooms require to be heated to a different level of comfort, for instance a Living Room tends to be warmer than a kitchen.

Both Watts (W) and BTUs (British Thermal Units) are units of energy / heat, but they come from different measurement systems.
A Watt is a unit of power (part of the Metric system) and in heating watts measure how much energy a heater produces.
A BTU is also a unit of energy, not power. Its an imperial measurement increasingly used less in the UK.
Since watts measure power and BTUs measure total energy, when talking about heating equipment, we usually use BTU per hour to compare directly to Watts.
1 watt = 3.412BTU/hr.
Don’t worry though our calculator gives both answers so you can shop radiators with the knowledge needed whatever measurement the manufacturers use!

Delta T =the temperature difference between the average temperature of the radiator and the room temperature. Its written as T50 T60 depending on what standard is used.
Radiator outputs depend strongly on the temperature difference. The bigger the Delta T the faster the heat leaves the radiator into the room.
Manufacturers often publish radiator outputs depending on where they were manufactured (Europe or older UK standard).
Don’t worry our handy calculator allows you to know what Delta you need to heat your room depending on how the manufacturer is publishing their output.