This calculator provides a high-level estimation based on the concepts of Manual J — the industry standard for residential load calculation. Proper sizing is critical; an undersized unit won't keep up on the hottest days, while an oversized unit will "short cycle," leading to poor humidity control and premature equipment failure.

Your equipment size is dictated by your building envelope. Upgrading from average to "Excellent" (R-49+) insulation can often reduce the required tonnage by 0.5 to 1.0 tons. Before buying new equipment, consider investing in air sealing and insulation to reduce the lifetime operational costs of your HVAC system.

Air conditioning isn't just about lowering the temperature (Sensible Cooling); it's also about removing moisture (Latent Cooling). In humid climates like Miami or Houston, the latent load is significantly higher. A unit that is too large will cool the air so quickly that it doesn't run long enough to remove the humidity, leaving your home feeling "cold and clammy."