Sizing an air conditioner or furnace by square footage alone is how homes end up with equipment that short-cycles, never dehumidifies, and dies early. This tool gives a fast, adjusted estimate of cooling tons and heating BTU from the factors that actually move the load. It is a sanity check, not a substitute for a full Manual J. Runs in your browser; nothing is uploaded.
Square footage is the single biggest driver of load, so a per-square-foot rule gets you in the neighborhood. But two identical 2,000 square foot houses can need very different equipment: one is a tight new build with good windows facing north, the other is a 1960s home with single-pane glass baking in west sun. Same floor plan, a ton or more apart in cooling load. This calculator adjusts the base rate for climate, insulation, windows, ceiling height, and occupants, which is why it will often disagree with a pure square-footage rule, and why it gets you closer.
The instinct to round up is the most expensive mistake in residential HVAC. An oversized air conditioner satisfies the thermostat on temperature before it has run long enough to pull humidity out of the air, so the house feels cold and damp and the system short-cycles itself to an early grave. Right-sizing means longer, gentler run times that actually dehumidify and sip less energy. That is the whole reason the trade sizes off a load calculation instead of a tape measure.
Once the size is settled, the job still has to be quoted, won, and billed. Present the replacement as a professional estimate with the equipment and load reasoning spelled out, and you become the contractor the homeowner trusts against two cheaper business cards. FieldForge turns that into a spoken sentence: say the scope and the invoice or estimate builds from your price book, captures the model and serial for the warranty record, and texts a payment link the moment the system is running. Print a quick one with the free HVAC invoice generator if you just need a clean document today.
Roughly 18 to 28 BTU per square foot depending on climate and construction, about one ton per 500 to 700 square feet. The calculator adjusts that base for your specifics.
Often around 3 to 4 tons in a mixed climate, but insulation, windows, and air sealing move it. Estimate above, then confirm with a Manual J.
No. It is a fast rule-of-thumb check. A full ACCA Manual J should size the equipment you actually install.