How accurate is the AC system size calculator?

It uses Florida-tuned BTU rules of thumb and is typically within 0.5 ton of a full Manual J. For installation we always perform an on-site Manual J.

Why is oversizing an AC bad in Florida?

Oversized systems short-cycle and don't run long enough to remove humidity, leaving the home cold but clammy. Right-sizing keeps indoor humidity around 50%.

How many square feet per ton of AC in Florida?

Typical Treasure Coast homes need roughly 500–600 sq ft per ton, adjusted for insulation, windows, sun exposure, ceiling height, and occupants.

AC System Size Calculator (Manual J Estimate)

Tell us about your home

Conditioned square footage

Living area only — exclude garage, lanai, and unconditioned spaces.

Average ceiling height

Attic & wall insulation

Number / size of windows

Sun exposure

Year built / envelope

Number of regular occupants

Heavy kitchen use (cooking daily, open kitchen, lots of appliances)

How AC Sizing Works

Why Florida homes need precise sizing

Hot, humid climate

Treasure Coast homes face 90°F+ days with 80%+ humidity for 6+ months a year. Your system has to handle sensible (temperature) and latent (moisture) loads at the same time.

Run-time matters

In Florida, longer run times dehumidify better. A right-sized system runs longer at lower stages and keeps your home at 50% RH. An oversized one short-cycles and leaves you damp.

Envelope drives everything

Insulation, windows, ductwork, and salt-air corrosion losses all affect the real load. A 1990s coastal home and a 2020 Tradition home with the same square footage can need different tonnage.

Frequently Asked Questions

How accurate is this calculator?

It uses Florida-tuned BTU rules of thumb adjusted for the variables that matter most in our climate. For a quick gut-check it's typically within 0.5 ton of a stamped Manual J. For a real install we always run the full Manual J on-site.

Why does ceiling height matter?

Higher ceilings mean more air volume to cool. A 10-foot or vaulted ceiling adds roughly 10% to the cooling load over a standard 8-foot ceiling.

Should I size up just to be safe?

No. Oversizing is the #1 humidity-comfort complaint we fix in Florida. A right-sized 2.5-ton system that runs 20 minutes will outperform an oversized 3.5-ton system that short-cycles every 5 minutes.

Does my old system size tell me what to buy?

Not always. Many existing systems were oversized at install or were sized before window/insulation upgrades. We Manual J every replacement to avoid carrying forward someone else's mistake.

Is this only for central AC?

The same load math applies to heat pumps and ducted mini-splits. For ductless multi-zone mini-splits we size each indoor head separately during the on-site visit.

Ready for a real Manual J?

Free in-home load calculation with every replacement estimate. No pressure, no gimmicks — just the right system for your home.

Request Free Estimate (772) 236-4277