Estimate cooling or heating load in watts, BTU/h, and refrigeration tons from floor area and a watts-per-square-metre rate.
| Load (W) | – |
| Load (BTU/h) | – |
| Tons | – |
Use this calculator for a first plant size from a rule-of-thumb load. Enter the floor area and watts per square metre.
Watts = area × W/m². BTU/h = watts × 3.412142. Tons = watts ÷ 3516.85. Area can be entered in square metres (m²) or square feet (ft²). The rate stays in W/m². A dwelling might be 50–100 W/m² depending on climate and fabric; this is not a Manual J or a heat-loss model.
This is a floor-area sketch. It does not add occupancy, solar, or ventilation separately.
Area: Conditioned floor area, in m² or ft².
Rate (W/m²): Load intensity in watts per square metre.
Load (W): Total load in watts.
Load (BTU/h): Same load in British thermal units per hour.
Tons: Same load in refrigeration tons.
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