Cooling Load & Tonnage Guide

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What a “Ton” of Cooling Means

One ton of air-conditioning capacity removes 12,000 BTU per hour of heat. The name comes from the heat it takes to melt one ton of ice in 24 hours. Residential condensers are commonly sold in half-ton steps (1.5, 2, 2.5, 3 …).

Why Sq-Ft-Per-Ton Varies

Hotter, more humid climates and leaky envelopes need more capacity per square foot (lower sf/ton). Milder cooling climates and better insulation need less (higher sf/ton). Ceiling height adds volume. Public contractor rules of thumb are often discussed around roughly 400–600 sq ft per ton, with some charts stretching toward ~800 in milder conditions. That band is what the calculator’s climate bases sit inside.

Energy Vanguard and ACCA’s HVAC blog have shown that real Manual J jobs — especially on newer, tighter homes — frequently land at much higher sf/ton (smaller equipment) than those old rules. Using 500 sf/ton on a modern house can install a system that is grossly oversized.

Why This Is Not Manual J

Manual J accounts for construction details, glass, orientation, infiltration, occupants, and internal gains room by room. A single sq-ft number cannot. Use the calculator to frame a conversation, then pay for Manual J before you buy. Full contrast: rule of thumb vs Manual J.

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