Radiator Configurator 2:0

Choosing the right radiator starts with knowing how much heat your room actually needs. Our radiator configurator with built-in BTU calculator makes it easy to work out the heat requirements of your room and find the right radiator to match.

What Size Radiator Are You Looking For?

Please complete all the required fields above before continuing.

FREQUENTLY ASKED QUESTIONS
What is a BTU calculator?
+
−
A BTU calculator is a tool that works out how much heat output you need to warm a room properly. It takes your room dimensions, wall construction and window details, then calculates how many British Thermal Units (BTUs) your radiator should produce.
How do I use a radiator BTU calculator for my room size?
+
−
It's simple. Enter your room's height, width and depth in metres, select your room type and wall construction, then add your window details. The calculator gives you your required watt output in seconds.
What is the best BTU calculator in the UK?
+
−
The best BTU calculator in the UK is one that accounts for room dimensions, wall construction, glazing and the number of outside walls. Our radiator configurator covers all of these, helping you find the optimum number of BTUs required for your room.
Are BTU calculators accurate enough to size a radiator?
+
−
BTU calculators are reliable for most domestic rooms. For complex projects, listed buildings or unusual layouts, we'd recommend getting in touch with our team for specific advice.
What is the difference between a BTU calculator and a heat loss calculator?
+
−
A BTU calculator is built to quickly estimate the heat output a single room needs. A heat loss calculator goes further, looking at the full thermal performance of a building: floors, ceilings, ventilation and more.

BTU calculator glossary

Heating terminology can trip you up, whether you're using our radiator configurator for the first time or you've been sizing radiators for years. This glossary covers the key terms you'll come across when using a BTU calculator or working out how much heat your room needs. It's here for homeowners, heating engineers and anyone planning a radiator project.

BTU (British Thermal Unit): A BTU is a unit of heat energy. It's the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. You'll see radiator output measured in BTUs because it helps you match the right radiator to your room.

BTU calculator: A BTU calculator is a tool that works out how much heat output you need to warm a room properly. You enter your room dimensions, wall construction and window details, and it calculates how many BTUs your radiator should produce.

Delta T: Delta T is the difference between the average water temperature inside your radiator and the air temperature in the room. It matters because it tells you the actual heat output under real conditions, not just laboratory figures.

Heat loss: Heat loss is the rate at which warmth escapes from a room through walls, windows, floors and ceilings. A BTU calculator uses this to help you pick a radiator with enough output to keep the room comfortable.

Heat output: Heat output is the amount of warmth a radiator produces, measured in BTUs or watts. Getting this right is what a BTU calculator is for: matching your radiator's output to what your room actually needs.

Watt: A watt is a unit of power used to measure radiator heat output. Our BTU calculator displays your required output in watts. One BTU per hour is roughly equal to 0.293 watts.  

For more guidance on heating, radiator care and choosing the right cast iron radiator for your home, have a look at our articles and guides on the Paladin blog.