HVAC Size & Tonnage Calculator
Estimate the cooling capacity required for your living space.
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Average (Standard building code)
Excellent (Energy efficient/New)
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Recommended System Size
— BTU
— Tons
How to Calculate HVAC Size
Choosing the right size for your Air Conditioning or Heating system is critical for both comfort and energy efficiency. An undersized unit will run constantly, failing to cool the home on hot days, while an oversized unit will "short cycle," turning on and off too quickly, which leads to high humidity levels and premature wear on the compressor.
The standard residential calculation follows several steps:
- Base Square Footage: Generally, you need about 25 BTUs (British Thermal Units) per square foot of living space.
- Ceiling Height: Standard calculations assume 8-foot ceilings. If your ceilings are higher, the volume of air increases, requiring more cooling power.
- Occupancy: Each person in a room adds approximately 400 BTUs of heat to the environment.
- Kitchens: Cooking appliances generate significant heat. A standard kitchen adjustment adds 4,000 BTUs to the total capacity requirement.
Understanding "Tons" in HVAC
In the HVAC industry, cooling capacity is often measured in "Tons." This doesn't refer to the weight of the unit. One ton of cooling is defined as the ability to remove 12,000 BTUs of heat per hour. Therefore, a 3-ton unit is rated for 36,000 BTUs.
Example Calculation
If you have a 1,500 sq. ft. home with average insulation:
- Base: 1,500 x 25 = 37,500 BTUs.
- If it has a kitchen: 37,500 + 4,000 = 41,500 BTUs.
- Tonnage: 41,500 / 12,000 = 3.45 Tons.
- Recommendation: You would likely look for a 3.5-ton system.