Complete Air Conditioner Sizing Guide
Choosing the right air conditioner size is critical for both comfort and energy efficiency. An air conditioner that is too small will run continuously, wasting electricity and shortening its lifespan without cooling the room. Conversely, an oversized unit will turn on and off too frequently (known as short-cycling), which fails to properly remove humidity, makes the room feel cold and damp, and increases wear on the compressor.
AC Sizing Chart (Standard Room Assumptions)
The table below provides a general sizing reference based on room square footage, under normal operating conditions:
| Room Area (sq ft) | Room Area (sq m) | Required Capacity (BTU/hr) | Recommended AC Tons |
|---|---|---|---|
| 100 – 150 | 9 – 14 | 5,000 – 9,000 | 0.75 Ton (9,000 BTU) |
| 150 – 250 | 14 – 23 | 9,000 – 12,000 | 1.0 Ton (12,000 BTU) |
| 250 – 350 | 23 – 32 | 12,000 – 18,000 | 1.5 Ton (18,000 BTU) |
| 350 – 450 | 32 – 42 | 18,000 – 24,000 | 2.0 Ton (24,000 BTU) |
| 450 – 600 | 42 – 56 | 24,000 – 30,000 | 2.5 Ton (30,000 BTU) |
| 600 – 800 | 56 – 74 | 30,000 – 36,000 | 3.0 Ton (36,000 BTU) |
Environmental Factors Influencing Heat Load
A simple area-based calculation is often insufficient because rooms absorb and generate heat differently. Our calculator factors in the following environmental variables to provide a more precise estimate:
- Sunlight and Roof Exposure: If the room has large west-facing windows or is directly under a concrete roof slab (top floor), it absorbs up to 10% more heat from solar radiation.
- Ceiling Height: High ceilings increase the total volume of air in the room. Standard sizing assumes an 8-foot ceiling. Additional height requires about 1,000 BTU per additional foot.
- Insulation and Drafts: Well-insulated rooms (double-glazed windows, insulated walls) keep the heat out, whereas rooms with thin brick walls or drafty doors require up to 25% more cooling power.
- Occupancy: Each person generates about 600 BTU/hr of body heat. Standard sizing assumes 2 people; add more capacity if the room is a shared living space or office.
- Kitchen Appliances: Stoves, ovens, and refrigerators generate a massive amount of ambient heat. Kitchen AC installations require an additional 4,000 BTU/hr buffer.
Inverter vs. Non-Inverter Air Conditioners
When buying an AC, you will choose between Inverter and Non-Inverter models. A **Non-Inverter AC** runs its compressor at 100% speed until the room temperature drops to the target, then shuts off. Once the room warms up, the compressor restarts. This cycles on/off constantly, causing temperature swings and massive power surges. An **Inverter AC** uses a variable-speed compressor that slows down once the target temperature is reached, maintaining it continuously at a low power state. Inverter ACs are quieter, maintain a steady temperature, and consume 30% to 50% less electricity, making them highly recommended for tropical regions like Bangladesh.