AC Sizing Calculator
What size air conditioner do you actually need? Answer 4 sets of questions — get a recommended tonnage range to sanity-check your contractor's quote.
⚠️ Bigger is NOT better
An oversized AC cools the temperature quickly but doesn't run long enough to remove humidity — leaving your home cool but clammy. Contractors sometimes oversize to avoid callbacks. This calculator helps you know what's right for your home before you sign anything.
Step 1: Basic Information
Total square footage of the space you're cooling
US state, or pick your climate type if outside the US
Each person adds heat load to the space
AC Sizing — Common Questions
What size AC do I need for a 1,500 sq ft house?
In a moderate climate with standard insulation, a 1,500 sq ft home typically needs 2.5 tons (30,000 BTU). In a hot climate like Florida or Texas, the same house may need 3 tons. With excellent insulation, a vented attic, and shading, 2 tons might be sufficient. The 'square footage only' rule misses too many variables — ceiling height, insulation, sun exposure, and construction type all matter significantly.
What size AC do I need for a 2,000 sq ft house?
Most 2,000 sq ft homes need 3–4 tons depending on climate and insulation. In the Southeast or South: plan for 3.5–4 tons. In the Midwest or Northeast: 2.5–3.5 tons. In very hot climates like Arizona or South Florida: 4–5 tons. Use the calculator above with your specific home details for a more accurate estimate.
Why does concrete block construction need more AC?
Concrete block (CMU) walls without insulation have a low R-value (about R-1.5 per 8-inch block) compared to insulated wood frame walls (R-13 to R-21). While CMU has high thermal mass that moderates daily temperature swings, the low R-value means significant heat eventually conducts through — especially after the sun has been heating the walls all day. In hot humid climates (Florida, Gulf Coast, Caribbean), uninsulated CMU homes often need more AC capacity than an equivalent wood frame home.
How much does attic insulation affect AC sizing?
Significantly. The attic accounts for 30–50% of a home's total cooling load in hot climates. A home with no attic insulation and a dark roof in a hot climate may need a system 30–40% larger than the same home with proper attic insulation (R-38+). Upgrading attic insulation before installing a new AC system can allow a smaller, less expensive unit to do the same job — often a better investment than oversizing.
Should I ask my contractor for a Manual J calculation?
Yes, always. Any reputable contractor sizing a new system should provide a Manual J calculation — the industry-standard method that accounts for all factors affecting cooling load. It typically takes 30–60 minutes to produce and gives you a defensible number. If a contractor just 'eyeballs' your square footage or says 'whatever you had before,' that's a red flag. The calculation should be done before any equipment is selected, not after.
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