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Air Conditioner Tonnage Calculator

Work out air conditioner tonnage instantly with clear inputs, formula shown and shareable results.

About Air Conditioner Tonnage Calculator

Cooling load starts from room volume at roughly 45 W per cubic metre, adjusted for solar gain and adding about 120 W per occupant. One ton of refrigeration is 12,000 BTU/h or 3.517 kW, so a typical 22 square metre room needs a little over one ton.

Formula

Cooling load

load = volume x 45 W/m3 x sun factor + occupants x 120 W; tons = BTU/h / 12000

Worked example

With the default values below, Air Conditioner Tonnage Calculator returns Cooling capacity required of 0.86. Change any input above and every figure here is recalculated in your browser.

Inputs used

Room area
22 m²
Ceiling height
2.7 m
Occupants
3 people
Sun exposureone of Shaded / north facing, Moderate, Heavy afternoon sun
Moderate

Results

Cooling capacity required
0.86 tons
Cooling capacity
10,349 BTU/h
Cooling capacity
3.03 kW
Estimated heat load
3,033 W

Step by step

  1. 1Values used
  2. 2Cooling load
  3. 3Cooling capacity required= 0.86 tons
  4. 4Cooling capacity= 10,349 BTU/h
  5. 5Cooling capacity= 3.03 kW
  6. 6Estimated heat load= 3,033 W

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is oversizing an air conditioner bad?

Yes. An oversized unit short-cycles, cooling the air quickly without removing humidity, leaving the room cold and clammy while wasting energy.

Why is a ton 12,000 BTU/h?

It is the cooling rate needed to melt one short ton of ice in 24 hours — a legacy of ice-based refrigeration.

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