HVAC Load Calculator

Roughly 18–30 BTU per square foot for cooling, depending on your climate. Hot, humid regions sit at the top of that range while cool, dry regions sit at the bottom. This tool adjusts the BTU-per-square-foot figure automatically based on the climate zone you select.

As a rule of thumb, one ton of air conditioning cools about 400–600 square feet, and the exact figure is climate dependent. In hot, humid climates a ton covers closer to 400 sq ft; in cool climates it can cover 600 sq ft or more. One ton equals 12,000 BTU/hr of cooling capacity.

No — this is a square-foot estimate, not a Manual J. Manual J is the ACCA (Air Conditioning Contractors of America) standard load calculation that accounts for window area, orientation, insulation R-values, infiltration, and duct losses. It is required by most jurisdictions for permits and is what a contractor should use for proper equipment selection. Use this tool for a quick ballpark only.

In a moderate climate this tool typically produces around 2.5–3 tons for a 1,500 sq ft house, but the real number varies with climate, insulation, ceiling height, sun exposure, and occupancy. Treat it as a starting point and confirm with a Manual J calculation.

A 2,000 sq ft house in a moderate climate usually lands around 3–3.5 tons with this estimator, but it varies based on your climate zone, insulation, window area, and other factors. A licensed contractor should run a full Manual J before sizing equipment.

An oversized air conditioner short-cycles — it cools the air quickly then shuts off before it removes enough humidity, leaving the home cold and clammy. Short-cycling also means higher energy costs and more wear on the compressor, shortening the unit's life. Right-sizing matters more than going big.

Yes. Hot and humid climates need more cooling capacity per square foot, while cold climates need more heating capacity. That is why this calculator uses different BTU-per-square-foot values for each climate zone — selecting the wrong zone will skew the estimate.

It is a rough estimate. The square-foot method ignores window area, orientation, ceiling insulation specifics, air infiltration, and duct losses, all of which change the real load. Use it to get in the ballpark; real equipment sizing needs a Manual J calculation performed by a licensed professional.

Yes, the calculator is completely free with no signup required. Your inputs are saved locally in your browser so they persist between visits — nothing is uploaded to a server. Clearing your browser data will erase your saved values.