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HVAC BTU Calculator — Air Conditioner Size for a Room

Estimate the cooling capacity needed for a single room. Enter the room dimensions and use the adjustments below to calculate BTU per hour, kW of cooling capacity and refrigeration tons.

Example: a 20 m² bedroom

A 5 m × 4 m room with a 2.4 m ceiling, two people and average sunlight has an area of about 215 ft². On the ENERGY STAR chart, this corresponds to a baseline near 6,000 BTU/h before additional adjustments. Enter your own conditions above to refine the estimate.

Related reading: Air Conditioners · ACH Calculator · Ventilation Calculator

How this calculator works

For room areas from 100 to 2,500 ft² (about 9.3–232 m²), the calculator uses the ENERGY STAR room-air-conditioner size table. It then applies ENERGY STAR adjustments for very sunny or shaded spaces, occupants beyond two, and kitchens. Ceiling heights above 2.44 m (8 ft) are scaled by relative room volume. Insulation factors are extra simplified assumptions, not part of the ENERGY STAR chart.

Smaller and larger rooms are outside the published size chart and should be assessed individually. The estimate is intended for single-room cooling, not heating or whole-building HVAC design. Room configuration, climate, humidity, windows, ventilation and equipment heat gains can change the real load. Do not use the result as a substitute for an ACCA Manual J or professional load calculation. Cooling capacity in kW is not electrical power consumption.

Source: ENERGY STAR — Room AC sizing guide (PDF).

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