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AC Tonnage Calculator: Which AC Size for My Room?

Enter room length, width and ceiling height, how sunny it is and how many people use it. You get the cooling load in tons and BTU/h and the standard AC size to buy.

Recommended AC size

1.5ton

Estimated cooling load
1.21 ton
In BTU/h
14,503 BTU/h
Room area
151 sq ft

Estimate only, based on standard thumb rules. Confirm quantities with your engineer or contractor before you buy.

Rounded up to the next common AC size.

Show working
  1. 150.7 sq ft ÷ 150 = 1.005
  2. × 1.094 × 1.1 = 1.21 ton

How to use

  1. Enter room length, width and ceiling height.
  2. Pick how much sun the room gets and tick top floor if the roof is above it.
  3. Enter the usual number of people to see the recommended tonnage.

Good to know

Thumb rule used by AC brands in India: about 1 ton for up to 150 sq ft at an 8–9 ft ceiling (Haier India buying guide, checked 27 Oct 2026). Higher ceilings scale up by height ÷ 9 ft; sunny south- or west-facing rooms add 10–20%; each person beyond two adds about 0.1 ton.

Here: tons = area ÷ 150 × max(1, ceiling ÷ 9 ft) × sun factor (1.0 shaded, 1.1 some sun, 1.2 very sunny) × 1.1 if top floor, + 0.1 per extra person. The result is rounded up to the next common size (0.75, 1, 1.5, 2, 2.5, 3 ton). 1 ton = 12,000 BTU/h.

It is an estimate. Kitchens, glass walls, many appliances, poor insulation or 45 °C+ summers may need more. An undersized AC runs flat out and cools poorly; a much oversized one cycles and dehumidifies badly. For large halls or offices, get a proper heat-load calculation.

Questions

Which AC for a 12 × 12 ft room?

144 sq ft is about 1 ton with a normal ceiling and little sun; choose 1.5 ton if it is a top-floor or west-facing room.

Is 1.5 ton enough for 180 sq ft?

Usually yes for a normal room: 180 ÷ 150 = 1.2 ton; with strong sun about 1.44 ton.

What is a ton in AC?

Cooling capacity of 12,000 BTU per hour (about 3.5 kW of heat removed), not weight.

Does an inverter AC change the size?

No. Size by heat load; an inverter AC just varies its speed to save power at part load.

Should I buy a bigger AC to be safe?

Slightly bigger is fine in very hot cities; much bigger wastes money and controls humidity poorly.

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