Your Room
Recommendation
The word "ton" in air conditioning has nothing to do with weight. It is a unit of cooling capacity: 1 ton equals 12,000 BTU (British Thermal Units) per hour of heat removed from the room. The term dates to the early twentieth century, when buildings were cooled with blocks of ice. Melting 1 ton (2,000 lb) of ice over 24 hours absorbs approximately 12,000 BTU per hour of heat from the surroundings. When mechanical refrigeration replaced ice, the unit carried over.
The same 1 ton of cooling capacity is the same everywhere: in London, Dubai, or Singapore, 1 ton always equals 12,000 BTU/hr. What changes with climate is how many square feet that capacity can effectively cool.
| Climate | BTU/sqft | 0.75 ton | 1 ton | 1.5 ton | 2 ton |
|---|---|---|---|---|---|
| Very Hot (>40°C) | 100 | up to 90 sqft / 8 m² | up to 120 sqft / 11 m² | up to 180 sqft / 17 m² | up to 240 sqft / 22 m² |
| Hot (33–40°C) | 75 | up to 120 sqft / 11 m² | up to 160 sqft / 15 m² | up to 240 sqft / 22 m² | up to 320 sqft / 30 m² |
| Warm (27–33°C) | 50 | up to 180 sqft / 17 m² | up to 240 sqft / 22 m² | up to 360 sqft / 33 m² | up to 480 sqft / 45 m² |
| Temperate (20–27°C) | 35 | up to 257 sqft / 24 m² | up to 343 sqft / 32 m² | up to 514 sqft / 48 m² | up to 686 sqft / 64 m² |
| Cool (<20°C) | 25 | up to 360 sqft / 33 m² | up to 480 sqft / 45 m² | up to 720 sqft / 67 m² | up to 960 sqft / 89 m² |
Always round up to the nearest standard size — never buy below the calculated requirement. Going one standard size above is acceptable and adds a useful buffer for peak-heat days. Going two or more sizes above causes short cycling: the AC reaches temperature in minutes, shuts off before removing meaningful humidity, and the room feels cold and clammy. Oversizing is not a conservative choice — it is a different problem.
When 1.5 ton is right and when 2 ton is right for the same 200 sq ft room:
A 130 sq ft bedroom in a hot climate (33–40°C), middle floor, west-facing windows, standard insulation, 2 occupants.
Required BTU: 130 × 75 × 1.0 (floor) × 1.15 (west windows) × 1.0 (insulation) = 11,213 BTU. Nearest standard size above 11,213 BTU: 12,000 BTU = 1 ton. However, 11,213 is close to the 12,000 ceiling — on a very hot day the 1 ton unit will be at its limit. In this case, 1.5 ton is the more comfortable choice as it provides a buffer.
What tonnage for a 150 sq ft room?
Cool climate: 0.75 ton. Temperate: 1 ton. Hot (S Asia, SE Asia): 1.5 ton. Very hot (Gulf): 1.5–2 ton depending on floor level and window exposure.
What does AC tonnage actually mean?
Cooling capacity, not weight. 1 ton = 12,000 BTU/hr of heat removed per hour. The term comes from the era of ice cooling: melting 1 ton of ice over 24 hours absorbs 12,000 BTU/hr.
Is 1.5 ton enough for a 200 sq ft room?
In a hot climate at middle floor: borderline — 1.5 ton works but 2 ton gives better buffer. In a cool or temperate climate: 1.5 ton is comfortable for 200 sq ft. Top-floor rooms with uninsulated roofs in hot climates need 2 ton for 200 sq ft.
Why do hot countries need more tonnage per sq ft?
The AC must overcome a larger temperature gap. In a cool climate peaking at 20°C, it fights a 4°C gap to maintain 24°C. In a 45°C climate, the same gap is 21°C — five times more heat flowing in per square foot per hour.
Does inverter AC need different tonnage?
No. A 1.5 ton inverter and 1.5 ton fixed-speed AC have the same rated cooling capacity. Tonnage selection rules are identical for both types. The inverter advantage is efficiency and electricity cost, not cooling capacity.
How does a top-floor room change the tonnage?
An uninsulated top-floor room needs 25–40% more tonnage. A flat concrete roof can reach 60–70°C and radiates heat into the room all afternoon. A 150 sq ft top-floor room in a hot climate that would be 1 ton on a middle floor may need 1.5 ton.
Should I go one size up for safety?
Round up at a boundary, yes. But deliberately buying two sizes up causes short cycling — poor humidity removal, cold-clammy feeling, and higher electricity use from frequent compressor starts. Accurate sizing is always better than oversizing.
Tonnage recommendations are based on the climate zone and conditions you select. Actual requirements vary with room construction, local climate, and usage patterns.