HVAC load calculator

A common rule of thumb is roughly 20–25 BTU per square foot in a moderate climate, adjusted for insulation, sun exposure, and ceiling height. For example, an average 1,800 sq ft home in a moderate climate needs around 36,000–45,000 BTU, or about 3 to 3.5 tons of cooling. This calculator estimates it from your specifics.

As a rough guide, plan on about one ton of cooling per 500–600 sq ft in a moderate climate — so a 1,800 sq ft home lands near 3 to 3.5 tons. Hotter climates, poor insulation, and lots of sun push that higher; well-insulated, shaded homes pull it lower. Use the calculator to adjust for your case.

No. This is a quick rule-of-thumb estimate for ballpark sizing and customer conversations — not a certified ACCA Manual J. A full Manual J accounts for window orientation, infiltration, duct losses, and more. Always run a proper Manual J before purchasing and installing equipment.

An oversized system short-cycles — it cools the air fast but shuts off before removing humidity, leaving the home cold and clammy, wearing out the compressor, and wasting energy. That is why correct sizing (a proper Manual J at install) matters more than simply "bigger is better."