The quick answer
For a normal room in Pakistan, plan on about 1 ton of cooling for every 150 square feet. Multiply the room's length by its width in feet, divide by 150, and round up to the next common AC size.
A 12 x 14 ft bedroom is 168 sq ft, which works out to about 1.1 ton, so a 1.5 ton AC is the safe choice. A 10 x 12 ft room (120 sq ft) is comfortably served by 1 ton.
| Room area | AC size | Typical room |
|---|---|---|
| Up to 150 sq ft | 1 ton | Small bedroom, study |
| 150 to 220 sq ft | 1.5 ton | Master bedroom, small office |
| 220 to 300 sq ft | 2 ton | Lounge, office room |
| 300 to 450 sq ft | 3 ton | Drawing room, shop |
| 450 to 600 sq ft | 4 ton | Hall, showroom |
What makes a room need more
The 150 sq ft rule assumes an ordinary room. Go one size up if two or more of these apply:
- Top floor, with the roof taking direct sun all day.
- West-facing walls or large windows that get afternoon sun.
- A kitchen, shop or office where many people or machines add heat.
- Ceilings higher than about 10 feet.
- Poor insulation or a room that is often opened to the outside.
Why bigger is not always better
An oversized fixed-speed AC reaches the set temperature quickly, then switches off before it has removed the humidity. The room feels cold but clammy, and the frequent on/off cycles waste electricity and wear the compressor.
An inverter AC softens this problem because it slows down instead of switching off, but it still costs more upfront for capacity you will rarely use. Pick the size the room needs, not the biggest you can afford.
Ton, BTU and kW: reading the label
1 ton of cooling equals 12,000 BTU per hour, or about 3.5 kW. Daikin model codes use the kW class: an FTXC50DV1B is a class 50 unit, rated at 17,400 BTU/h, which is about 1.5 ton.
Rated capacity can differ slightly from the round number sellers use. On our product pages we show both the tonnage and the official BTU/h figure from Daikin's catalog.
Large spaces: when a wall AC is not enough
Beyond about 300 sq ft, one wall unit struggles to spread air evenly. Halls, showrooms and open offices are better served by a floor standing unit, a ceiling cassette or a ceiling suspended unit. For whole buildings, consider VRV or ducted systems.
Frequently asked questions
Is 1 ton enough for a 12 x 12 room?
A 12 x 12 ft room is 144 sq ft, so 1 ton is enough for a normal room. If it is on the top floor or gets strong afternoon sun, choose 1.5 ton.
What size AC do I need for a 20 x 15 lounge?
That is 300 sq ft, so a 2 ton AC is the usual choice. If the lounge is sunny or busy, consider 2.5 ton or a floor standing unit.
Does inverter vs non-inverter change the size I need?
No. Size the AC for the room first, then choose inverter or non-inverter based on how many hours a day you run it.
