Radiator BTU Calculator
Use our handy BTU calculator to find the radiator heat output you need, based on your room size, windows and insulation. For larger spaces, you may need more than one radiator.
Once calculated, we’ll recommend suitable radiators to match your results. All of our radiator BTU values are clearly listed online and in-store to help you choose the right option.
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- What is a BTU? BTU is used to measure heat. It shows the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. When it comes to heating, the BTU value tells you how powerful a radiator is and how much warmth it gives off.
- What does BTU stand for? BTU stands for British Thermal Unit. It’s a heat measurement used to compare how much energy heating appliances like radiators can produce.
- What BTU do I need? The BTU you need depends on the size of your room, how many windows it has, and how well insulated it is. A small, well-insulated room needs less heat than a large or draughty one. The easiest way to work it out is by using our free BTU calculator tool above. Simply enter a few details and get instant radiator recommendations.
- What is the difference between BTU values at DT30 and DT50? BTU values change depending on the temperature difference between your room and the water flowing through your heating system. This is called Delta T (ΔT).
- DT30 is based on older heating systems with cooler water.
- DT50 is now the most common standard for UK homes and gives a more realistic idea of radiator performance.
If you're comparing radiators, make sure you're looking at the same Delta T value. - What does BTU at Delta T65 mean? Delta T65 (ΔT65) is a higher temperature difference used mainly in commercial or high-temperature systems. It shows how much heat a radiator gives off when the water in the system is much hotter than the room. Most UK homes use Delta T50 instead, so check which one is being used when comparing BTUs.
- How many BTU are in a kW? 1 kilowatt (kW) is equal to 3,412 BTU.
- What is a good BTU for radiators? There’s no one-size-fits-all answer. The right BTU depends on your room size, insulation, and layout. But it’s not just about the BTU value. Different radiator materials and designs affect how efficiently heat is delivered. For example, aluminium radiators heat up fast, cast iron holds heat for longer, and double-panel models emit more heat than single-panel ones.
To make things simple, use our BTU calculator. It works out what your room needs and recommends suitable radiators with the right heat output.