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BTU Calculator
Room Heat Calculator

Radiator BTU Calculator

Choosing the right radiator or towel warmer for you bathroom or living rooms within your home is important not only in style but also to make sure your room remains warms. Radiators come with an output value measured in BTU's  (British Thermal Unit), but how do you know what size BTU you need?

Our heat output or 'BTU'calculator make it easy for you to work out how much radiator power you need. There are several factors which can affect this, such as room dimensions, heating levels and types of window, which are all covered in our radiator BTU calculator below.

Choosing the right radiator can help reduce your energy bills. For example, too large a radiator will increase bills unnecessarily, and too small a radiator won't provide enough heat and will be constantly running at maximum. By using our BTU calculator you can establish your Watt / BTU outputs required for a particular room to ensure that your room(s) will be heated comfortably and efficiently.

1. Select measurement type
Metric (metres) Imperial (feet)
2. Your room dimensions
Height of room:
Width of room:
Length of room:
Window Area x2:
3. Type of room:
4. What is below the room?
5. What is above the room?
6. Select type of outside wall:
7. Select type of window:
8. Select number of outside walls:

Bathroom Radiators

Bathroom Radiators

Bathroom Radiators come in many different shapes, styles and sizes. The most popular bathroom radiators are Towel rails or towel warmers, sometimes called ladder radiators, which not only add a head source to your bathroom but also help to dry and keep your towel warm.



Radiators are an essential part of modern life that we've come to rely on. The convenience of a radiators and central heating has replaced the open fire to heat our homes. Central heading radiators are what gets most of us through those cold winter months.

Designer Radiators

Designer Radiators

Designer and feature radiators work just as well as standard radiators while providing a modern feel to the room they're used in. On the contrary, our range of traditional radiators is perfect for keeping the feel of older houses and giving an industrial look.

Radiator Valves

Radiator Valves

Radiator valves allows you to control the flow of hot water and heat output of an individual radiator. This means each radiator in each room can be set to its own desired temperature. Radiator valves are available in different shapes and style to suit the different situation.

How to choose the right radiator(s) for you room

BTUs are ‘British Thermal Units’, the unit in which radiator efficiency is measured. Factors such as room dimensions, window size and wall material are used to calculate the required outputs of radiators, in order to adequately heat a room.

Use our BTU Calculator to determine the heat requirements of your room. Simply enter the details in the corresponding fields and we’ll show you how many BTUs you need to ensure your space is always warm, cosy and inviting.

How to calculate the BTUs for your room

The best way to get an accurate calculation is to enlist the services of a plumber. However, BestHeating's BTU calculator is a good guide as to what level of BTU and Watt output will efficiently heat your room. Please note: the calculated figure is for the combined heat output of all radiators and/or towel rails in your room (larger rooms may require more than one).

When purchasing a towel radiator, its also good practic to ad 15% extra t your BTU requirements to allow for heat soak from towel on the radiator.

Fitting TRV Valves

Its good practice to purchase radiators that are over the BTU required ranther than under or Close to the heat require. By purchasing slightly over BTU requirements, the use of TRV (Thermostantic Radiator Valves) will keep the room at a comfortable temprature.

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