AC Tonnage Calculator
Instant results as you type.
ft
Recommended AC size (tons)
1
Cooling needed (BTU/hour)11,400
Room area (sq ft)120
What this meansAbout 11400 BTU/hour, so a 1 ton unit. Going a size larger is not better — an oversized air conditioner cools fast, switches off before it removes humidity, and leaves the room cold and clammy.
Air conditioner sizing is where most online calculators quietly mislead Indian buyers: they apply a North American rule of about 20 BTU per square foot, which suits a mild summer and a well-insulated house, and recommends roughly a quarter of what an Indian room needs. This calculator uses a baseline that reproduces the tonnage Indian dealers actually quote, then adjusts for ceiling height, sun exposure and how many people are in the room.
How to use it
- Enter the room length, width and ceiling height.
- Say how many people usually use the room, and how exposed it is to sun.
- Read the recommended tonnage and the underlying BTU figure.
Examples
- A 12 x 10 room, two people, normal sun: about 11,400 BTU — a 1 ton unit.
- A 15 x 15 top-floor west-facing room with four people: about 26,100 BTU — 2.5 tons.
Frequently asked questions
- What size AC do I need for my room?
- As a general guide in Indian conditions: up to about 120 sq ft takes 1 ton, up to 180 sq ft takes 1.5 tons, and up to 250 sq ft takes 2 tons. Those are starting points — a top-floor room under a hot slab, a west-facing wall, or a room that regularly holds several people needs more, which is what the adjustments here are for.
- Is a bigger AC always better?
- No, and this is the most common sizing mistake. An oversized unit cools the air quickly and then switches off before it has removed the humidity, leaving the room cold and clammy. The short cycling also wears the compressor and wastes electricity. Correct sizing beats generous sizing.
- Does a top-floor or west-facing room need more?
- Considerably. A west-facing wall takes the full afternoon sun, and a top-floor room sits under a slab that has been absorbing heat all day. Either can raise the cooling load by around twenty per cent, which is often the difference between a 1.5 and a 2 ton unit. Select heavy exposure for these.
- What is a ton of cooling?
- It is 12,000 BTU per hour — historically the cooling a ton of ice provides in a day. It describes cooling capacity, not the weight or power draw of the unit. Efficiency is separate, measured by the star rating, and that is what decides your electricity bill for a given tonnage.