AC size calculator (BTU and tons)
Enter the room area in square meters to get an approximate cooling capacity and the nearest common AC size.
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How to use it
- Enter room area, btu/h per m², sun exposure, usual number of people and the room is a kitchen.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
BTU/h = area × BTU per m² × sun factor (0.9 shaded, 1.1 sunny) + 600 per person above two + 4000 for a kitchen. Tons = BTU/h ÷ 12000.
Example
Inputs: Room area = 20 m², BTU/h per m² = 700 BTU/h per m², Sun exposure = Normal, Usual number of people = 2, The room is a kitchen = no. Result: Cooling capacity needed: 14,000 BTU/h; In tons: 1.17 tons; In kilowatts: 4.1 kW.
Limits and caveats
- The default 700 BTU/h per m² is a rule of thumb for hot Gulf summers; moderate climates often use about 20 BTU/h per ft² (roughly 215 per m²).
- The sun, occupant and kitchen adjustments follow ENERGY STAR guidance for room air conditioners.
- Insulation, high ceilings and large windows change the load; a proper load calculation needs an HVAC engineer.
Questions about this tool
How many tons do I need for a 20 m² room?
At 700 BTU/h per m² you need about 14,000 BTU/h, around 1.17 tons, so a 1.5 ton (18,000 BTU/h) unit fits.
How many BTU are in one ton?
One ton of refrigeration is 12,000 BTU/h by definition, the heat needed to melt one short ton of ice in 24 hours.
Is a bigger AC always better?
No. An oversized unit cycles on and off, removes less humidity and wastes energy, so choose the nearest size above your need.