Quick answer
Cooling capacity in kW = room area × the chosen W/m² load assumption ÷ 1,000. Divide kW by 3.51685 for refrigeration tons. A 25 m² room at an illustrative 150 W/m² gives 3.75 kW, about 12,796 BTU/h or 1.07 tons; that assumption is not a Qatar sizing standard.
Read a room-size chart as a sensitivity check
The table holds a deliberately illustrative 150 W/m² input constant to show the unit conversions. It is not a recommended load density for Doha, Dubai or Riyadh. If the correct room load is known from a calculation, use that instead of adopting this demonstration number.
One refrigeration ton equals 12,000 BTU/h, approximately 3.51685 kW of cooling capacity. Cooling kW is not electrical input kW. Energy use also depends on equipment efficiency, operating conditions and runtime.
| Room area | Cooling kW | BTU/h | Refrigeration tons |
|---|---|---|---|
| 15 m² | 2.25 | 7,677 | 0.64 |
| 20 m² | 3.00 | 10,236 | 0.85 |
| 25 m² | 3.75 | 12,796 | 1.07 |
| 30 m² | 4.50 | 15,355 | 1.28 |
| 40 m² | 6.00 | 20,473 | 1.71 |
Worked example: 25 m² top-floor Doha bedroom
Start by recording the 5 × 5 m floor area, actual ceiling height, exterior-wall and roof construction, windows and orientation, shading, intended indoor conditions and occupancy. A top-floor room with exposed roof and afternoon glazing should not inherit another room's assumed factor without a load assessment.
To see the uncertainty, compare 100, 150 and 200 W/m² as arbitrary scenarios: the 25 m² room becomes 2.5, 3.75 or 5.0 kW, about 0.71, 1.07 or 1.42 tons. These scenarios show how much the answer depends on the input; they do not establish a permissible range for purchasing a unit.
The equivalent room area is about 269.10 ft². A unit conversion cannot fix an unsupported rule of thumb. Supply the room survey to the installer or engineer and request the design load and the chosen unit's performance at the applicable outdoor condition.
What a room load calculation includes
A proper assessment considers heat transfer through the envelope, solar gains, air leakage and ventilation, internal heat sources and moisture load. Ceiling height matters through geometry and air volume, but multiplying area by a universal height correction is not a replacement for this assessment.
Ask how adjacent rooms are treated and whether doors stay open. A majlis with intermittent occupancy, a bedroom and a kitchen are different cases. Exhaust fans and outdoor-air supply also affect how much outside air the system must condition.
Split, ducted and window systems
System type changes distribution, installation and control. A ducted design must account for duct routing, losses, air balance and return paths. A split system still needs suitable placement, drainage and service access. A window unit needs the correct opening and safe installation details.
Compare the capacity available under your design conditions, not only the product's nominal tonnage label. Ask for the selected model, relevant rating conditions, sensible and latent capacity information where applicable, efficiency, noise and commissioning scope.
Why simply buying larger can disappoint
The U.S. Department of Energy explains that oversizing can cause frequent cycling and poor humidity removal. That is a useful warning for humid conditions; it does not establish the exact capacity your GCC room needs.
Use this worksheet to understand units and discuss assumptions. Before purchasing, get a documented load assessment and equipment selection. Check that the contractor will verify operation, condensate drainage and airflow at commissioning, rather than treating the printed tonnage as the entire job.
Questions people ask
Is one ton enough for a 20 m² room in Qatar?
Area alone cannot establish that. Calculate the room's actual heat and moisture loads and compare the chosen unit's available capacity at local design conditions.
Does 3.5 kW cooling mean 3.5 kW electricity use?
No. Cooling capacity and electrical input are different ratings. Electrical demand depends on the equipment and operating efficiency.
Can I use the furnace BTU calculator for cooling?
No. A heating rule of thumb is not a cooling calculation. Use the cooling scenario tool for conversions and obtain an actual cooling-load assessment for selection.
Sources and calculation basis
Source links support the specific technical points below. Worked quantities are Construclytic calculations using the assumptions shown above. References do not establish local prices or replace the project specification.
- U.S. DOE: consumer guide to heating and coolingExplains why area-only sizing rules miss climate and building performance.
- U.S. DOE: purchasing efficient room air conditionersDiscusses oversized units, cycling and humidity removal; not a GCC capacity table.