BTU Calculator
Calculate the ideal BTU cooling or heating capacity for your room. Estimates based on room size, ceiling height, insulation, and sun exposure.
Room Dimensions
Environmental Factors
How to Calculate BTU for AC
BTU (British Thermal Unit) is the standard unit for measuring thermal energy. When choosing an Air Conditioner, matching the BTU capacity to your room size is crucial.
- Too Small: The unit will run continuously, failing to cool the room and wasting energy.
- Too Large: The unit will cycle on and off too frequently (short cycling), failing to dehumidify the air and wearing out the compressor.
The Formula
A basic rule of thumb is 20 BTU per square foot. However, our calculator uses a more precise volume-based formula that accounts for ceiling height:
Base BTU = Volume (cubic feet) × 4
Adjustment Factors
- Sunlight: If the room is very sunny, we increase capacity by 10%. If shaded, we decrease by 10%.
- Occupancy: Humans generate heat. We add approx. 600 BTU per person.
- Kitchens: Appliances like ovens and fridges add significant heat. We add 4,000 BTU for kitchens.
Common AC Sizes
- 5,000 - 6,000 BTU: Small rooms (100-250 sq ft)
- 8,000 - 10,000 BTU: Medium rooms (300-450 sq ft)
- 12,000 BTU (1 Ton): Large rooms (500-600 sq ft)
- 18,000 BTU (1.5 Ton): Multi-room spaces (700-1000 sq ft)
? Frequently Asked Questions
In HVAC, 1 Ton represents the cooling capacity of melting 1 ton of ice in 24 hours. It equals 12,000 BTU/hr.
Yes! Heat rises, and there is more air volume to cool in a room with high ceilings. A standard square footage calculation assumes 8ft ceilings; our calculator adjusts for height.
It is not recommended. An oversized AC cools the air too quickly without removing humidity, leaving the room feeling damp and clammy.