Radiator BTU Calculator

Find the perfect radiator for any room. Our calculator helps you determine the precise British Thermal Unit (BTU) output you need to keep your space warm and energy-efficient.

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Room Details

Room Dimensions (in metres)
Room & Wall Type
LayoutGrids & Insulation

Your Results

Total BTU Required

1,212 BTU/hr

Recommended Radiators

1 standard radiator

Based on a standard radiator output of 5,000 BTU.

This is an estimate. Always consult a qualified heating engineer for a precise assessment before purchasing.
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Understanding Your Radiator Needs

What are BTUs?

A British Thermal Unit (BTU) is the standard measurement of heat output from a radiator. The higher the BTU rating, the more heat the radiator produces. Our  calculator estimates the total BTUs needed to heat your room to a comfortable temperature, accounting for heat lost through walls and windows.

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Choosing the Right Size

Once you have your BTU requirement, you can choose a radiator or combination of radiators that meet this value. It's better to slightly exceed the BTU requirement than to fall short. For large rooms, using two radiators placed strategically can provide more even heating than one very large one.

The Importance of Insulation

Good insulation makes a huge difference. A well-insulated room with double-glazing will retain heat for longer, meaning you need a smaller, more energy-efficient radiator. Improving your home's insulation can lead to significant savings on your heating bills. See how much you could save with our gas cost calculator.

Different Room, Different Needs

A living room where you spend lots of time needs to be warmer than a bedroom. Kitchens and bathrooms often need a higher BTU output to counteract tiles and cooler surfaces. Our calculator adjusts the formula based on the type of room you select to give a more tailored recommendation.

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Frequently Asked Questions

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