Northgate Heating & Air
Free tool

AC Sizing Calculator

A first-pass estimate of the tonnage your home needs, adjusted for Florida's climate. Real installs still get a full Manual J load calc — but this gets you in the ballpark before you get quotes.

Insulation
Windows
Exposure
Recommended size
3.5 tons
42,000 BTU/h
Based on ~500 sq ft per ton for your inputs. Actual sizing requires a Manual J load calculation.
Round to the nearest available size (0.5 ton).
Never oversize — undersize by half a ton beats over.
Two-stage or variable-speed helps humidity control.

Why this calculator is honest about its limits

Contractor sizing rules of thumb are usually wrong for humid climates. This tool tries to be honest: it uses square footage as the starting point, but adjusts for the four factors that most change the answer in Volusia County — insulation depth, window area, ceiling height, and coastal salt / sun exposure.

What it can't do: replace a proper Manual J load calculation, which measures your specific home's heat gain by room. If you're replacing a system, insist on a real Manual J before your contractor quotes tonnage.

Common sense checks

  • If the calculator says 5 tons for a 1,500 sq ft home, something is off.
  • If the calculator says 2 tons for a 3,500 sq ft home, ditto.
  • Oversizing hurts humidity control. Undersizing hurts on peak-heat days. Both matter.

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