BTU Calculator helps you determine the necessary heating or cooling capacity calculated in BTUs/h. So you can know exactly what radiator or air conditioning unit power works for your house. Calculating your house's heating requirements has never been easier. Do you know how to calculate BTU or what is a BTU? Below the BTU Calculator you can find more information on how to determine the amount of energy you need to heat or cool your house. Enjoy!


Width: *
Length: *
Height: *
Room type: *
Other factors:
Width: *
Length: *
Is there a kitchen in the space? *
How many persons use the room? *
Other factors:

Disclaimer: Please note that the calculations produced by this tool do not pretend to be 100% accurate. It is intended solely for general information and education purposes. The creator of this calculator is in no way liable of any actions which might be taken by users of this calculator.

The BTU Calculator is a quick way to determine the heating or cooling requirement for a specific space and could be considered guidance in choosing the right equipment. 

What is a BTU?

A British Thermal Unit (BTU) is the measure of energy required to heat 1 pound of water 1 degree Fahrenheit. One BTU is roughly equal to 1,055 Joules. 1BTU/hour is equal to 0.293 watt. BTUs are the standard measurement of heat output needed to heat any structure, therefore can measure radiator power.

The amount of BTUs required depends on many variables including the dimensions of the room or space, the destination of that space, construction variables such as degree of insulation and even on climate factors. A simple use of the BTU Calculator can help you know the energy necessary for heating or cooling your home. The BTU Calculator already adjusts the basic BTU calculation depending on your answers about the factors influencing the efficiency of the heating or cooling system.

The capacity of furnaces and air conditioners is given in BTUs per hour. You need to establish the correct number of BTUs for your house needed to either heat or cool it. The methods differ for heating and cooling and are described below.

How to calculate the total BTUs needed for home heating?

Do you know how many BTUs are needed to heat a room? The BTU requirement will be for the whole room, so you need to calculate the total amount of space the room covers. To do that you need to measure the length, width and height of the room so you can then calculate the cubic footage of each room by multiplying the length, width and height of the room. L*l*h= cubic footage;

To get a basic estimate of the BTU heating requirement you then multiply the cubic feet by 3, 4 or 5 depending on the destination of the room starting with 3 for kitchens and common rooms, 4 for bedrooms and children rooms and 5 for dining and living rooms. The BTU requirement will then be adjusted accordingly to other factors that can influence the heating of the room. Poor home insulation, the existence of large windows, rooms with many exterior walls will determine a higher BTU requirement so increase your calculation by 10%-20%.

On the other hand, a new, well insulated house with double glazed windows, and south facing rooms will lower the BTU heating requirement so don't forget to lower your BTU calculation by 10%-20%.

But how is the required amount of BTUs to heat a room calculated if you want to increase the temperature in that room with a certain amount of degrees? You can easily determine the BTU requirement in this case by multiplying the cubic footage by 0.133 and by the desired temperature increase. This will give you the final number of BTUs that you need to increase the temperature in your room by the desired number of degrees.

How to calculate how many BTUs are needed to cool a room?

First we need to understand what cooling capacity means. The cooling capacity of an air conditioning unit os measured in BTU/h and represents the ability of that unit to remove heat from a certain space. Knowing the exact cooling capacity for your space helps you choose an appropriate air conditioning unit.

The first step to calculate the total BTUs needed for home cooling is to measure the length and width of the space. Then use the obtained square footage to determine the BTU requirement by consulting a specialised chart on cooling energy. Here is one below:

Between Approximate BTU/h
Square footage ~ Min Square footage ~ Max
100 150 5,000
150 250 6,000
250 300 7,000
300 350 8,000
350 400 9,000
400 450 10,000
450 550 12,000
550 700 14,000
700 1000 18,000
1,000 1,200 21,000
1,200 1,400 23,000
1,400 1,500 24,000
1,500 2,000 30,000
2,000 2,500 34,000

Once you have the basic BTU value for your space adjust this value according to the existence of a kitchen in the place (you need to add 4,000 BTU in this case). The Chart value is calculated for a space shared by two people. For each extra person add an extra 600 BTUs. You should also reduce the BTU cooling requirement by 10% if the space to be cooled is heavily shaded or add 10% to the BTU cooling requirement if the place is very sunny. Knowing the BTU requirement for cooling your space can help you choose the right air conditioning unit.

18 Oct, 2013 | 0 comments | 3620 views

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