Calculate the size your air conditioning 

There are a number of complex and involved calculations are design engineers make when sizing an air conditioning system for a premises. A fundamental neccessity is that the cooling output of the air conditioner is greater than the heat gain of the space it intends to serve. Our cooling calculator will give you an approximate value for this heat gain, measured in BTUs (British Thermal Units), and help identify the most appropriate cooling solution.

How it works

The heat load of a building or room is calculated by adding together the heat gain from individual items. At it’s more simple the major factors are :

The size of the area being cooled
The size of the space that requires cooling
Window sizes and positions
The number of people who occupy the space
Heat from electrical equipment, machinery and plant
Heat from lights

Our engineers have very sophisticated tools and computer modelling software to measure heat loads. They will take into account a number more factors than detailed above, for example shading to windows, location of premises and building construction and thermal properties. However for a quick, simple and approximate indication of what your heat load (and so cooling requirement) might be we have created a cooling calculator for your use. Please note that the calculator assumes a reasonable level of insulation to walls, roof or ceiling.  It is also only an approximate check of heat gain and does not replace the need for expert advise and detailed heat load calculation.

Get started on your system

The fields marked * are required for minimum estimate.

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Room Measurements:

* Width: m
* Length: m

Window Measurements (total of each face):

Window area (North facing)
Window area (South facing)

Room Use and Type:

Number of occupants

Electrical equipment/lighting:

The wattage is normally written on the equipment or light. 1kw = 1000w.
Total Equipment Wattage
Total Lighting Wattage
Total BTU/hr
Total Watts/hr
Total Kw/hr


This calculator is provided for a quick and approximate check of heat loads. It should not be considered as a replacement for expert advice or a precise and detailed heat load calculation. For this you should contact us. Whilst we have taken every precaution to help ensure this calculator is accurate, we accept no responsibility or liability resulting or howsoever arising from its use.