BTU / AC Size Calculator
Find the air conditioner capacity a room needs in BTU, tons or kW, using ENERGY STAR sizing guidance.
About the BTU / AC Size Calculator
ENERGY STAR's sizing chart matches room area to capacity, then adjusts: reduce by 10% for a heavily shaded room, add 10% for a very sunny one, add 600 BTU for each regular occupant beyond two and add 4,000 BTU for a kitchen. An oversized unit cools quickly but removes less humidity.
The formula
Base BTU from area chart × sun factor + 600 × (people − 2) + 4,000 (kitchen)
ENERGY STAR room sizing
| Area (ft²) | Capacity (BTU/h) |
|---|---|
| 100–150 | 5,000 |
| 150–250 | 6,000 |
| 250–300 | 7,000 |
| 300–350 | 8,000 |
| 350–400 | 9,000 |
| 400–450 | 10,000 |
| 450–550 | 12,000 |
| 550–700 | 14,000 |
| 700–1000 | 18,000 |
| 1000–1200 | 21,000 |
| 1200–1400 | 23,000 |
| 1400–1500 | 24,000 |
| 1500–2000 | 30,000 |
| 2000–2500 | 34,000 |
Worked example
Example: Cooling capacity = 7,000 BTU/h
- Inputs: Units: ft²; Room area: 280; Sunlight: Normal; People who regularly use the room: 2; It's a kitchen: No.
- Formula: Base BTU from area chart × sun factor + 600 × (people − 2) + 4,000 (kitchen)
- Result: Cooling capacity = 7,000 BTU/h
Questions people ask
What is a ton of cooling?
12,000 BTU per hour, the heat to melt a ton of ice in a day.
How do I convert to kW?
1 kW = 3,412 BTU/h.