ac capacity based on room size

Recently I was sitting in my small study room, thinking whether 1 ton AC is enough for a small room, like a small bedroom. Because nowadays people are going for a 1.5 ton AC for their rooms due to good sales pitches. That is why this thought crossed my mind and I researched the topic thoroughly and kinda found the answer.

A 1 ton inverter AC is perfect for a small room that is approx. 100 to 120 sq. ft. No direct sunlight, less than 3 people in the room & room height <12 feet. Also, the need for concrete roof, no extreme climates, and less metal furniture in the house (preferably wooden furniture).

Factors to be considered while deciding Tonnage of AC:

Extremely hot weather (>45 degrees)Add extra 0.5 ton
Terrace flat or direct sunlightAdd extra 0.5 ton
Heat producing work at homeAdd extra 0.5 ton
Type of furnitureDepends on type
Rooms where papers or books are moreAdd extra 0.5 ton
Long  or heighted house (>12 feet)Add extra 0.5 ton
Inverter stabilizer used along with the ACEverywhere except Metropolitan cities
Basic capacity is 100 sq ft/ 600 = 0.167Add 0.5 Ton for every 5 ppl

Basic factors to consider while buying an AC

A 1 ton AC is enough for what room size?

It is very important to calculate the right tonnage for your room. First and foremost find out the area of your room in square feet.

Secondly divided by 600 to get the basic capacity. For example, if you have a room which has an area of hundred square feet, then:

100/600 = 0.167

Later on, you have to add 0.5 ton for every 5 people in the room. Ultimately you get your required tonnage for your room.

Normally a 0.8 ton AC will be proper for 100 square feet room into (it’s a small room).

Some additional factors to be added

Extremely hot weather

If you stay in extreme weather, for example more than 45 degrees then add an extra 0.5 ton, for better cooling and effectiveness.

Terrace flat or direct sunlight

If your flat is on the top floor or it is a bungalow or a cottage type house with an open terrace, then add an extra 0.5 ton or more.

Heat producing work at home

If heat producing work is done at your place then it will cause extra load on the AC. In such cases it is better to use a higher ton AC.

Type of furniture

The furniture in your home definitely varies the load on your AC. One type of classification in furniture by wood and metal.

  • For rooms with wooden furniture 100 square feet room you can use 1 ton AC
  • More wooden furniture 120 square feet room you can use 1 ton AC
  • For wooden furniture > 190 square feet room you can use a 1.5 ton AC
  • More wooden furniture >300 square feet room you can use 2 ton AC
  • Metal furniture and 120 square feet room use 1.5 ton AC
  • Use 2 ton AC for Metal furniture and 190 square feet room

Now it is clear that more metal furniture absorbs the heat as well as the cold in the room. It is better to have wooden furniture than metal furniture. Also the less furniture in your room the better and more efficient the functioning of the AC.

Rooms where papers or books are more

Basically, more papers or books generate more heat in the room. This implies that a small room will require a higher capacity AC to cool the room.

For example for a hundred square feet room where normally one ton AC would be enough you will have to use a 1.5 ton AC. Also a 200 square feet room where 1.5 ton AC would be enough will require a 2 ton AC.

This proves that you require an AC with higher load for rooms with papers.

Type of roof on the house

Different types of houses in different locations have many types of roofs. The roof can be either an asbestos/ false ceiling or temporary roof or it can be a permanent concrete roof.

If the house has an asbestos ceiling then the AC will not work for 120 square feet. A one ton AC will work only till a hundred square feet area. This is provided that the windows are closed properly and the doors have rubbers below them and on the sides.

Long or heighted house

A 1-ton AC will not be able to cool properly until the end of the room. So what you can do is use a Tower fan in between so that air flows till the corners of the room. Or else use a 1.5 Ton AC.

Inverter stabilizer used along with the AC

In cities where power cuts do not happen like metropolitans you don’t require a stabilizer or inverter. All other cities except metropolitans will require an inverter or stabilizer.

How much area does a 1 ton AC cover?

This is based on the BTU (British thermal units).


  • 0.8 ton AC uses 9000 BTU;
  • 1 ton AC uses 12000 BTU;
  • 1.25 ton AC uses 15,000 BTU;
  • 1.5 ton AC uses 18000 BTU.

Now I have one formula that I will give you which will help you calculate your suitable BTU AC.

Area of your room in square feet x 25 BTU will give you the BTU of your room.

For example 110 square feet x 25 = 2650 BTU.

However, this is not all. There are some more factors that you have to consider.

If the room is in the shade(no direct sunlight) then you will have to reduce 10% in the total BTU.

For each additional person in the room add 600 to 700 BTU to the total

Kitchens in a house are comparatively hotter so add more 2000 to 3000 BTU.

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What if I already have a 1.5 ton AC in a small room?

Sometimes it happens because of a good sales pitch. This is what happened to me recently. The salesman advised a 1.5 ton AC for a standard room. After installing that I found that the AC was actually more than what was required for my room. In fact the room was totally freezing.

So what I did is I opened the adjacent room and the AC started cooling both the rooms.

These days the 1.5 ton AC that I purchased is used for cooling two rooms at a time. Only caveat here is that I have made sure that there is no air passage on the outside or any microleakage is in the air.

So what does this incident have to do with the topic of interest of this article?

Basically this personal experience made me feel that a 0.8 ton AC is enough to cool that room if people inside are less than 4.Therefore it is clear that a small room needs 0.8 ton AC.

What if my room size is 12 by 12 or the room’s height is more?

For a 100-130 square feet room 0.8 to 1 ton AC is enough. for a room of 130 square feet to 200 square feet of 1.5 ton AC is better. more than 182 200 square feet rooms require a 2 ton AC and more than 500 square feet rooms require more than one AC in multiple places.

How efficient is a 1 ton AC for my budget?

Many times we have faced the option of buying a smaller capacity AC or higher capacity AC. It’s a total dilemma where in a smaller capacity will find it difficult to cool the room in and lead to increased electricity bills. On the other side, more than required capacity AC will also increase the electricity bill because of higher consumption. So you have to properly size the air conditioner according to your room.


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In the above discussion, you must have noticed that it takes more than general knowledge for a person to decide upon the perfect AC. There are a number of scenarios that can play themselves out if you don’t go deep and analyze the situation.

You may undershoot for a low capacity AC, as compared to your room size. On the flip side, you may go overboard and buy one with extra high capacity. In either of the cases, you will face the issue of excess use of electricity than required. All of these can lead to a bad outcome : rise in electricity bills.

Wisdom says it is better to look before you leap. But, as you saw in the paragraphs above, there are a ton of different factors to consider before you can finalize, plus the brand name also. That is why we have come to your rescue. We have done an exhaustive compilation of helpful resources across the internet and additional research offline to give you the best tips and tricks.

Hope it helps. For any doubts, corrections or additions just comment below.

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