Find your AC size
AC Tonnage Calculator
Find the right AC size for your room
Recommended AC size
1.5 ton
Estimated cooling load: 14,143 BTU (1.18 ton raw)
AC tonnage by room size — complete chart
“Standard” assumes medium sun exposure and a non-top-floor room. “Best case” and “worst case” show how much a shaded room or a top-floor, direct-sun room can shift the recommendation.
| Room size | Best case | Standard | Worst case | BTU/hr (standard) |
|---|---|---|---|---|
| 80 sq ft | 0.8T | 0.8T | 0.8T | 7,543 |
| 100 sq ft | 0.8T | 0.8T | 1T | 9,429 |
| 120 sq ft | 1T | 1T | 1.5T | 11,314 |
| 150 sq ft | 1.5T | 1.5T | 1.5T | 14,143 |
| 180 sq ft | 1.5T | 1.5T | 2T | 16,971 |
| 200 sq ft | 1.5T | 2T | 2T | 18,857 |
| 250 sq ft | 2T | 2T | 2T | 23,571 |
| 300 sq ft | 2T | 2T | 2T | 28,286 |
| 400 sq ft | 2T | 2T | 2T | 37,714 |
| 500 sq ft | 2T | 2T | 2T | 47,143 |
Beyond 191 sq ft, our calculator caps its recommendation at 2 ton — see “Large rooms” below for why splitting into two units is usually the better move past this point.
1 ton AC — how much area does it cover?
Under standard conditions, 1 ton covers rooms up to about 127 sq ft (roughly an 11×12 ft room). A shaded, lower-floor room can sometimes stretch a little further on 1 ton; a top-floor room with strong sun crosses into 1.5-ton territory sooner — as early as 107 sq ft.
1.5 ton AC — room size in feet
1.5 ton is India's most common domestic AC size. Under standard conditions it covers roughly 128–190 sq ft.
Coverage range (standard conditions)
128–190 sq ft
e.g. a 12×15 ft (180 sq ft) bedroom or small living room
1.5 ton = 12,000 × 1.5
18,000 BTU/hr
the standard worldwide unit for cooling capacity
When to choose 1.5 ton over 1 ton
Large rooms & halls (300+ sq ft)
Our calculator caps its single-unit recommendation at 2 ton. For genuinely large or open-plan rooms, a single large AC isn't always the best answer — two smaller units are a well-established alternative.
Air distribution
Large or L-shaped rooms often have dead zones a single AC can’t reach evenly. Two units placed on opposite walls cool the whole space more consistently.
Redundancy
If your one large AC needs servicing, you lose all cooling. With two units, you keep partial cooling while one is repaired.
Running cost
Two inverter units running at partial load are often more efficient than one large unit running flat out, especially in mild weather.
How to calculate AC tonnage — step by step
- 1Measure your room length and width in feet, and multiply to get the area. Example: 12 ft × 15 ft = 180 sq ft.
- 2Divide the area by 140 to get the baseline tonnage. 180 ÷ 140 = 1.29 ton.
- 3Add 10% for medium sun exposure, or 20% for strong/direct sun. Medium sun: 1.29 × 1.1 = 1.41 ton.
- 4Add a further 10% if the room is on the top floor. Top floor: 1.41 × 1.1 = 1.55 ton.
- 5Round up to the nearest standard size — 0.8, 1, 1.5 or 2 ton. 1.55 rounds up to 2 ton.
AC ton to BTU conversion
The universal formula
1 Ton = 12,000 BTU/hr
Ton → BTU
Multiply tonnage by 12,000
1.5 Ton × 12,000 = 18,000 BTU
2.0 Ton × 12,000 = 24,000 BTU
BTU → Ton
Divide BTU by 12,000
18,000 ÷ 12,000 = 1.5 Ton
24,000 ÷ 12,000 = 2.0 Ton
Undersized vs. oversized vs. correctly sized
Undersized AC
Runs continuously at full load, never quite reaches the set temperature on hot days, and wears the compressor faster.
Oversized AC
Cools the room quickly then shuts off (short-cycling) before properly dehumidifying — the room feels cool but clammy.
Correctly sized AC
Runs steady cycles, maintains temperature and humidity, and gives the lowest running cost for the room.
Once you know your tonnage
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Frequently asked questions
What size AC do I need for a 150 sq ft room?
A 150 sq ft room typically needs a 1.5 ton AC under standard conditions (medium sun, not top floor) — our calculator returns 1.5 ton for exactly this size. If the room is heavily shaded, 1 ton can suffice; if it's on the top floor with strong afternoon sun, stick with 1.5 ton rather than downsizing.
How much area does 1 ton AC cover?
Under our standard assumptions (medium sun exposure, not top floor), 1 ton covers roughly up to 127 sq ft, with the recommendation stepping up to 1.5 ton beyond that. A shaded, ground/middle-floor room can sometimes stretch a bit further; a top-floor room with strong sun needs the upgrade sooner.
Does floor level affect AC tonnage?
Yes. A top-floor room absorbs direct heat through the roof all day, so our calculator adds 10% to the cooling load for top-floor rooms compared with an identical room lower in the building.
Does window/sun exposure matter for AC sizing?
Yes. Rooms with strong direct sun (west-facing, large unshaded windows) need more cooling capacity than shaded rooms. Our calculator adds 10% for medium sun exposure and 20% for high/direct sun exposure.
Is a bigger AC always better?
No. An oversized AC short-cycles — it cools the room quickly and shuts off before properly dehumidifying, leaving the room feeling cool but clammy, and wears the compressor with frequent on/off cycling. An undersized AC runs continuously at full load, struggles to hit the set temperature on hot days, and uses more electricity than a right-sized unit. Correct sizing gives the best comfort and running cost.
What size AC do I need for a large room (300+ sq ft)?
Our calculator caps its recommendation at 2 ton — the largest commonly available single-unit residential size — for rooms with a standard-conditions load at or beyond 191 sq ft. For genuinely large or open-plan spaces (300–500 sq ft and up), two smaller AC units placed for even air distribution usually cool more evenly and give you backup capacity if one unit needs servicing, rather than relying on one oversized unit.
How is AC tonnage related to BTU?
1 ton of AC cooling capacity equals 12,000 BTU/hr (British Thermal Units per hour) — this is the international standard used to rate cooling capacity, regardless of brand.
How accurate is this AC tonnage calculator?
It uses a widely-used rule of thumb — roughly 1 ton per 140 sq ft — adjusted for sun exposure and floor level. It is a planning estimate, not a substitute for a professional heat-load (Manual J style) assessment, which also accounts for ceiling height, insulation quality, number of occupants, and local climate in detail.