AC Tonnage Chart: What Size AC by Square Footage

Here's the chart everyone searches for, followed by the adjustments that keep it from steering you wrong. Tonnage measures cooling capacity — 12,000 BTU per hour per ton — and matching it to your home is the single highest-stakes decision in the entire AC purchase. More expensive to get wrong than any brand or efficiency choice.

The Chart

The Adjustments That Move the Number

• Ceilings over 8 feet: add capacity proportionally — a 10-foot ceiling is 25% more air to cool
• Poor insulation / older construction: size toward the high end of the range
• Big west-facing glass: afternoon solar gain can add a half-ton of real load
• Shade, good insulation, tight construction: size toward the low end
• Second floors and bonus rooms over garages: chronic hot spots are usually duct problems, not tonnage problems — fix airflow before upsizing
• Kitchen-heavy or high-occupancy homes: people and appliances are load too

The Oversizing Trap (Read This Before Rounding Up)

When two sizes look possible, the instinct is to take the bigger one. In humid climates that instinct is expensive: an oversized AC hits the thermostat setpoint fast and shuts down before it's pulled the moisture out of the air. You get a cold, damp house, mold-friendly humidity, constant compressor cycling, and a shorter system life. Undersizing by a little shows up as long runtimes on the hottest days; oversizing punishes you every single day. When genuinely between sizes in a humid climate, take the smaller one — or better, get the load calculated properly.

Don't Copy the Old Unit's Label

The system you're replacing was sized by someone too — possibly wrong, possibly for a house that's since gained insulation, new windows, or an addition. If the old unit short-cycled and the house felt clammy: it was too big. If it ran flat-out and never caught up: check ducts and insulation before assuming too small.

The Bottom Line

The chart gets you to the neighborhood; your home's specifics pick the house. Send us your square footage, ceiling height, and basics through the form below — we'll size it properly and send wholesale pricing on the right system, no visit, usually within the hour.