Understanding AC Sizing
Air conditioner size is measured in **Tonnage**, where **1 Ton** equals the removal of **12,000 BTUs (British Thermal Units)** of heat per hour. Choosing the correct size is crucial: an oversized unit wastes energy and doesn't dehumidify properly; an undersized unit runs constantly and fails to cool the space.
Industry Standard Sizing Chart (Approximate)
Rule of Thumb by Area (for Average Climate)
| Area (Sq Ft) | Tonnage Needed |
|---|---|
| 400 - 600 | 1.5 Tons |
| 601 - 1000 | 2.0 Tons |
| 1001 - 1400 | 2.5 Tons |
| 1401 - 1800 | 3.0 Tons |
| 1801 - 2400 | 4.0 Tons |
| 2401+ | 5.0+ Tons |
Factors for Detailed Load Calculation (Manual J)
- **Climate Zone:** Hot, humid regions require a larger unit for the same square footage.
- **Ductwork Condition:** Leaky ducts can significantly reduce efficiency and cooling capacity.
- **Ceiling Height:** Vaulted or high ceilings increase the total volume of air to be cooled.
- **Appliance Heat:** Kitchens and rooms with large electronics (servers, multiple PCs) require a higher BTU.
- **Roofing Material:** Dark-colored roofs absorb more solar heat than light-colored roofs.
Important Note: Manual J
The most accurate way to size an AC unit is through a $\mathbf{Manual\ J\ Load\ Calculation}$, performed by an HVAC professional. This calculator uses generalized formulas and should only be used for preliminary budgeting or planning.