How to Choose the Right AC Capacity for Your Room Size

The most common mistake we see is choosing AC capacity based on floor area alone. Area matters, but it is not the only factor.

Area is the starting point

Calculate area = length x width in metres. A 4 x 5 metre room is 20 square metres. That number is where sizing starts.

Why does the floor level matter?

A room on the top floor sits directly under the roof, which absorbs sun all day and radiates heat inward. That is why the same area on the top floor needs more capacity than the same area on a middle floor.

Why does orientation matter?

A sun-facing room gets direct sunlight for longer, so its heat load is higher than a shaded room. That alone can push you up one capacity step.

What happens if you get the size wrong?

Too small: the unit runs continuously without ever reaching the set temperature, so your bill goes up and the unit is pushed beyond its rating.

Too large: it cools fast then shuts off and restarts — short, repeated cycles wear the compressor, and it does not remove humidity properly, so the air feels cold but clammy. On top of that you paid more than you needed to.

Other things to consider

• Number and size of windows, and whether they are insulated.
• Ceiling height — high ceilings need more capacity.
• How many people regularly occupy the space.
• Heat-producing sources nearby (an open kitchen, lots of electronics).

The fastest way

We built a free calculator where you enter your room size, orientation and floor, and it gives you the right capacity along with the available units instantly. For special cases, always consult an engineer before buying.