9,000 BTU/h is the most popular capacity among home split air conditioners. But "how many m² does it cool" has a more nuanced answer than the box suggests.
Quick rule of thumb
Industry standard: 330-380 BTU per m². 9,000 BTU divided by that range = 23-27 m² under standard conditions.
What "standard conditions" means
- Ceiling height 2.5-2.7 m
- 1-2 windows facing east or north
- Modern insulation (buildings post-1990)
- 1-2 occupants
- Standard electronics (TV, laptop)
When to upsize
Each factor below typically needs +15-20% capacity:
- South/west facing windows: +20%
- Ceilings above 3 m: +15%
- Kitchen heat sources (stove, oven): +25%
- 4+ permanent occupants: +10% per person
- Old single-pane windows: +20%
Practical examples
Bedroom 18 m², north-facing, 2 occupants → 9,000 BTU fits comfortably.
Living room 25 m², south windows, 3 people → 9,000 BTU is insufficient; upsize to 12,000 BTU.
Office 20 m², 4 PCs, 4-5 staff rotation → recommend 12,000 BTU (heat sources).