BTU Calculator

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FAQ's

BTU or British Thermal Unit - is the amount of heat needed to increase the temperature of 1lb (one pound) of water by one degree Fahrenheit. This is the imperial measurement, your Installer may work using metric values for this calculation; Watts. Either can be used to choose your radiator.

With radiators, the BTU measurement refers to how much energy is required to heat a room. The higher the BTU is, the greater the radiator’s heat output will be. How effective the radiator will be though, depends on factors such as the size of the room and how well insulated it is. A radiator’s ability to transfer heat will depend on its material, size and surface area as well as the water temperature within the system.

Delta T, or ∆T, specifically relates to the difference in temperature between the water circulating in the central heating system and that of the room or ambient temperature.

Flow in 75°C ,Flow out 65°C = Average water temperature inside radiator is 70°C.

If the room or ambient temperature is 20°C and the average water temperature inside the radiator is 70°C, the Delta T or ∆T value is calculated as 70°C - 20°C = 50°.

A Delta T correction factor allows end users and professionals to find out the actual output of a radiator or towel rail in the range of Delta T variations.

Eastbrook provides Delta T 30° & Delta T 50° outputs. You can use the listed correction factors below to find the actual output at Delta T 60° and other Delta T’s listed below:

ΔT	Correction Factors
70°	1.548
65°	1.406
60°	1.268
50°	1
45°	0.871
40°	0.747
35°	0.627
30°	0.513
25°	0.404

Example: Assuming a radiator or towel rail has a heat output of 750 Watts at ΔT (delta T) = 50°. At ΔT (Delta T) = 60°, the output would be 750 x 1.268 (from the table above) equating to 951 Watts.

Calculator

* = Mandatory field.

Please input all measurements in metres.

Room Type*

Height(M)*
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Width(M)*
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Length(M)*
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Window Area (m2)*
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What is below this room?

What is above this room?

Type of outside walls?

Type of windows?

Number of outside walls?

Please correct the above issues before calculating

Results

Required BTU @ΔT50°C:

Required Watts:

You may need more than one radiator to meet the required BTU output.

View matching heating products here

warning Disclaimer: Our calculations are only estimated and are based on information you provide. Our BTU Calculator can only process the most common factors that affect heat loss and may not take into account all factors relating to your particular requirements. Any results provided by our BTU Calculator should not be considered 100% accurate and we accept no liability for any errors resulting from the estimates given.

For completely accurate BTU requirements, we recommend you to refer back to your heating engineer.

All towel rail/radiator outputs are based on Delta T 50°C (ΔT50°C).

warning Please Note: this is a guide only. A radiator with insufficient output may never raise the surface temperature of the radiator to the required level. Outdoor temperatures, external walls, insulation, heated adjacent rooms (i.e. above, below, and to the side) all have a contributing effect. The boiler should have sufficient capacity to supply all connected radiators to the sum of their maximum demand. Larger rooms such as living rooms may require more than one radiator, positioned evenly throughout the room. If this is the case, simply divide the required output between the number of radiators needed.