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BTU / Watts Calculator
Our BTU (British Thermal Units) Calculator is a handy guide to help you choose the right radiator for your room. A radiator that’s too big wastes heat and costs more to run, while one too small overworks and isn’t warm enough. Choosing the right size saves you energy and money.
Which room you are heating?
What are the dimensions of the room?
Your BTU result
@ΔT50°C
0 BTU
0 watts
BTU calculations are estimates based on your input and may not cover all factors. We recommend consulting a heating engineer for accuracy. Results should be used as a guide only, and we cannot be held liable for any errors.
Recommended radiators for your BTU
How do I choose the right radiator?
All our radiators have their heating outputs labelled on them so It’s easy for you to find the right size cast iron radiator for your room.
Our top tips for heating your room.
Get a radiator with a slightly higher BTU than what is required.
We would always recommend where possible choosing a radiator with an output slightly higher than what is required as you can always decrease the temperature it gives out, but you can’t increase its maximum output if the radiator is too small.
Install Thermostatic Radiator Valves (TRVs)
You can install Thermostatic Radiator Valves (TRVs) to automatically control the temperature of each radiator. They sense the room temperature and adjust the hot water flow, increasing or decreasing heat output as needed. This improves energy efficiency and helps reduce heating costs.
Balance Multiple Radiators in Larger Rooms
For bigger spaces, relying on a single high-BTU radiator can lead to uneven heating, with some areas staying too warm while others remain cold. Instead, consider installing multiple smaller radiators positioned strategically to ensure consistent heat distribution throughout the room. This approach also prevents one radiator from overworking and helps maintain a comfortable, balanced temperature.
Check for Obstructions
A radiator’s efficiency depends on proper airflow. Placing it behind furniture, curtains, or other obstructions can trap heat, preventing it from warming the room effectively. To maximize performance, ensure your radiator has enough clearance, allowing warm air to circulate freely. If space is limited, consider wall-mounted or multiple smaller radiators to provide effective heating without taking up too much room.
