Free tool
Air Cooler Size Calculator: How Many Litres — and Why That Is the Wrong Question
What size air cooler does your room need?
Coolers are sized on how much air they move, not on tank litres. This works out the air delivery your room needs, then tells you what tank size gives you the run time you want.
A standard Indian room is 10 ft.
Delhi/Jaipur ≈ 30-40%. Mumbai/Chennai ≈ 70-80%.
Air delivery needed
1,274 m³/hr
at 30 air changes an hour
Format to look at
Personal cooler
Tank for 8 hr run
≈ 10 L
evaporates ≈ 1.3 L/hr
Method: required airflow = floor area × ceiling height × air changes per hour ÷ 35.315. Tank size is derived from evaporation at roughly 1 litre an hour per 1,000 m³/hr of airflow in dry heat, so it is a run-time figure, not a measure of cooling power.
| Room | Floor area | Air delivery needed | Format |
|---|---|---|---|
| Study / small bedroom | 100 sq ft | 850 m³/hr | Personal cooler |
| Standard bedroom | 150 sq ft | 1,275 m³/hr | Personal or tower |
| Large bedroom | 200 sq ft | 1,700 m³/hr | Desert or tower |
| Living room | 300 sq ft | 2,550 m³/hr | Desert cooler |
| Large hall | 500 sq ft | 4,250 m³/hr | Large desert cooler |
| Shop floor (40 ACH) | 800 sq ft | 9,060 m³/hr | Industrial cooler |
| Factory bay (60 ACH) | 2,000 sq ft | 33,980 m³/hr | Industrial, often multiple units |
Almost every air-cooler listing in India leads with tank capacity, and almost every buyer therefore treats litres as a measure of power. It is not. A 90 litre tank and a 50 litre tank can carry identical blowers; the larger one simply runs longer before someone has to fill it. What actually decides whether the far side of the room cools is the volume of air the unit moves each hour, how far it throws that air, and how well the pads transfer water into the airstream. Air delivery in cubic metres per hour is the number that captures the first of those, and it is the number this calculator gives you.
The air-changes-per-hour method used here is the standard approach for evaporative cooling, and it differs from how an air conditioner is sized for a good reason. An AC recirculates and cools the same air in a sealed room, so it is sized on heat load in BTU. A cooler works by replacing the room's air with cooler, more humid outside air, so it is sized on how quickly it can turn that air over. That is also why ventilation is part of the sizing rather than an afterthought: with no path for air to leave, the air changes do not happen at any airflow.
One limitation worth stating plainly. This calculator sizes for airflow, and airflow is only half of evaporative cooling — the other half is how dry the incoming air is, which is set by your climate and not by anything you can buy. A perfectly sized cooler in 75% humidity will still disappoint, which is why the tool gives you a humidity verdict alongside the number rather than quietly producing a recommendation that cannot work.