What this calculator does
The Cooling Load Calculator estimates how much cooling power an air conditioner needs to keep a room comfortable. Enter the room's floor area and describe the room — insulation quality, sun exposure, number of people, and whether it is a kitchen — and the calculator returns the cooling load in BTU/h, kilowatts (kW), and refrigeration tons, the three figures used to size air conditioners worldwide.
It is a rule-of-thumb estimator, ideal for choosing between a 9,000 and a 12,000 BTU unit, or between a 1.5 and a 2.5 kW split system, before you talk to a supplier. The page is available in English, Arabic, and Spanish.
How to use the Cooling Load Calculator
- Enter the room area and choose square meters or square feet. To get the area, multiply the room's length by its width. Calculate each room separately — every room needs its own cooling.
- Choose the insulation quality. "Good" means a modern, well-insulated building; "average" is a typical home; "poor" means thin walls, single glazing, or a very hot climate.
- Choose the sun exposure. "Sunny" for rooms with large or west/south-facing windows that get direct sun, "shaded" for north-facing or heavily shaded rooms, and "average" otherwise.
- Enter the number of people who regularly occupy the room, and tick the kitchen box if the room is a kitchen (cooking appliances release a lot of heat).
- Click "Calculate" to see the required cooling load in BTU/h, kW, and tons of refrigeration.
Formulas
The calculator uses the standard rule-of-thumb method for sizing room air conditioners:
The final BTU/h figure is always rounded up to the next 100, and the kW and ton figures are rounded up to one decimal, so the estimate errs on the safe side: a slightly larger unit always covers the load, while an undersized one runs constantly and never reaches the set temperature. One refrigeration ton equals 12,000 BTU/h and one kilowatt equals 3,412 BTU/h.
Examples
- A 20 m² bedroom with average insulation and average sun, occupied by 2 people: 20 × 215.3 = 4,305.6 → 4,400 BTU/h ≈ 1.3 kW ≈ 0.4 tons. The next standard size up, a 9,000 BTU unit, is a comfortable choice.
- A 35 m² living room with poor insulation and sunny windows, occupied by 5 people: 35 × 215.3 × 1.25 × 1.1 = 10,360, plus 3 × 600 for the extra people = 12,160 → 12,200 BTU/h ≈ 3.6 kW ≈ 1.1 tons — an 18,000 BTU split system would fit well.
- A 15 m² kitchen with average insulation and average sun: 15 × 215.3 + 4,000 (kitchen) = 7,229 → 7,300 BTU/h ≈ 2.2 kW ≈ 0.7 tons.
- Imperial: a 250 ft² bedroom with good insulation and shaded windows, 1 person: 250 × 20 × 0.85 × 0.9 = 3,825 → 3,900 BTU/h ≈ 1.2 kW.
Frequently asked questions
What is a cooling load?
The cooling load is the amount of heat that must be removed from a room per hour to keep it at a comfortable temperature. It comes from the sun, the walls and roof, people, appliances, and outside air leaking in. Air conditioners are rated by how much heat they can remove per hour, expressed in BTU/h, kilowatts, or tons of refrigeration.
How many BTU do I need per square meter?
About 215 BTU/h per m² (20 BTU/h per ft²) for an average insulated room. Poorly insulated or very sunny rooms need up to 25–30 BTU/h per ft², while well-insulated shaded rooms can manage with about 17.
Does this replace a professional load calculation?
No. This is a rule-of-thumb estimate for choosing a room air conditioner or split system. Professionals use detailed methods (such as ACCA Manual J) that account for window areas, wall construction, orientation, ducts, and local design temperatures. For whole-house systems, ask an HVAC professional.
What if my ceiling is unusually high?
The rule of thumb assumes a normal ceiling of about 2.4–2.7 m (8–9 ft). For very high or vaulted ceilings, treat the room as one size larger — for example, add 10–20% to the result — because there is more air volume and wall area to cool.
What size air conditioner should I buy?
Air conditioners come in standard sizes — 9,000, 12,000, 18,000, 24,000 BTU/h (or 1.0, 1.5, 2.5, 3.5 kW). Pick the first standard size that is equal to or larger than your calculated load. Do not oversize dramatically: a unit that is too big cools quickly but leaves the air humid.
Can I use it for several rooms at once?
Calculate each room separately. Rooms have different sun exposure, occupancy, and insulation, and each room needs its own cooling. If you are sizing one unit for an open-plan space, use the total area and the worst-case sun exposure of the space.
Is my data saved or sent anywhere?
No. Every calculation runs in your browser, and nothing you type is stored or sent to a server.
Related calculators
Other free calculators commonly used with this tool: Wet Bulb Calculator, Heat Pump Calculator, and Solar Load Calculator.
Want a deeper walkthrough? Read our cooling load guide.