The full form of BTU is British thermal unit. Being the basic unit of thermal energy, it has replaced joules in the scientific circles (the SI unit). All materials that are combustible must have a BTU. Many countries have accepted the BTU as the standard gauge for measuring the energy consumed or spent depending on the state.

The BTU per square foot is mostly used for calculating capacity for an air conditioner to cool a room. This varies with the size of the room along with a variety of other factors, which are endemic to the location. The BTU per square foot needs to be calculated very carefully and the question as to why can be addressed when we can understand the functions of an air conditioner. An air conditioner cools a room and removes the prevalent humidity. However, if you install one, which is either too big or too small for the size of the room, then it will not be able to function efficiently leaving its job undone and the occupants dehydrated and uncomfortable. Hence, it is important to calculate the BTU for the air conditioner taking into consideration the size of the room.

Other factors that need to be considered are the placement of the room with respect to the location of the larger building. It should also be considered that the effect of the summer heat or climate with regards to the geographical location. The numbers of people who occupy the said area along with the different equipments present in the room that generates heat and the amount of make up air needed are all factors that should be taken into consideration when calculating the BTU per square feet.

Air conditioners are not the only areas in which BTU per square feet are considered. The BTU per square feet is also used to describe the energy volumes of various heating and cooling devices, the burning of fuels in equipments such as stoves, furnaces etc. Another major area where the BTU per square foot is important is in power plants. The calculation of the BTU per square foot is an important aspect that all energy sectors are looking into. This is because with the increased awareness of the environmental and climatic issues, more emphasis is given to create progressively highly efficient systems. One of the major and the most domestic application of the calculation of the BTU per square foot are when it comes to personal computers. This is because with the advent of faster and more powerful computers, the heat generated by the systems is higher and hence the need to calculate the BTU per square foot.

BTU is British thermal unit. It is the unit used for measurement of heat energy. It is actually the amount of heat energy required to increase temperature of 454g (1pound) of water to one degree Fahrenheit. BTU has been replaced nowadays with other energy unit, JOULE. Although it has been used in some countries including Canada. It is mostly used in power, heat, air conditioning and steam generation industries. Actually BTU gives idea that how much amount of heat is required to cook something. All combustible items have their own BTU ratings, like charcoal has 9,000 BTUs per pound.

If BTU is compared with joules and calories than one BTU is almost equal to 251.9 calories and 1055 joules. BTU per square foot is used to measure the capacity of air conditioner to cool the room. Because if capacity of air conditioner is not measured then it might cause discomfort because it will not be able to remove humidity from the room.

In order to measure BTU per square foot of your room. Firstly measure length and width of your room with measuring tape. Multiply length with the width, so you will get the area of room in square foot. Now compare the size of room with list of BTUs for air conditioner. This list is made by U.S Department of Energy for air conditioner BTU capacity. You can get the desired result by matching your room's square foot with BTU capacity. Considerations are requiring if the room is sunny or shady. Similarly if the person in room is more than two then add 600 BTUs per person and if air conditioner is for kitchen then add 4,000 BTUs, as kitchen has more heat.

For instance 10,000 BTU Window Air Conditioning units are capable of cooling a 500 square foot of room. So it's better to keep in mind that 20 BTUs are required per square foot. Consider for example, if your room to be cooled is about 15 x 30 you would have a 450 square foot space to cool, thus would require a 9,000 BTU units.

BTU is not only specifically used for air conditioners but also used to describe the energy volumes of various devices like stoves furnaces etc. BTU in square foot is also useful in power plants. Nowadays most important used of it is in computers. As faster and efficient computers are discovered so heat generated by them is also increasing. Thus requires proper calculation of BTU per square foot.