Home Comfort Tools
Answer 4 plain-English questions about your home. We give you the right AC size in tons, your BTU range, and tell you exactly why.
Updated May 2026
This is the answer for a typical 1500 sq ft home in a mixed climate. Change any input above and click the button to see your number.
Your 1500 sq ft home in a mixed climate with average insulation needs about 30,000 BTU per hour of cooling. That is a 2.5 ton air conditioner. The standard starting point is 20 BTU per square foot, then adjusted up or down for how hot your summers get and how well your home holds temperature. Three bedrooms is a normal household so no extra adjustment is needed.
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Here are the most common combinations people ask about. These use the mixed-climate baseline with average insulation and 3 bedrooms. Use the calculator above for your specific situation.
| Home Size | Hot Climate (FL/TX/AZ) | Mixed Climate | Cold Climate (MN/WI/NY) |
|---|---|---|---|
| 1,000 sq ft | 2.0 tons | 1.5 tons | 1.5 tons |
| 1,200 sq ft | 2.5 tons | 2.0 tons | 1.5 tons |
| 1,400 sq ft | 2.5 tons | 2.0 tons | 2.0 tons |
| 1,500 sq ft | 3.0 tons | 2.5 tons | 2.0 tons |
| 1,800 sq ft | 3.5 tons | 3.0 tons | 2.5 tons |
| 2,000 sq ft | 4.0 tons | 3.5 tons | 3.0 tons |
| 2,400 sq ft | 5.0 tons | 4.0 tons | 3.5 tons |
| 3,000 sq ft | 6.0 tons | 5.0 tons | 4.0 tons |
Table assumes: 3 bedrooms, average insulation (1980-2010 construction). Add half a ton for older/poorly insulated homes. Subtract half a ton for new construction with good insulation.
Are you an HVAC contractor or need the technical Manual J version? Use our HVAC Load Sizing Calculator for BTU/hour, tonnage, climate zone multiplier, window count, and door load. Contractor-grade, all 8 IECC zones, voice readback for job sites.
One ton of cooling equals 12,000 BTU of heat removed per hour. The word "ton" comes from the old days of using ice blocks for cooling. One ton of ice melting over 24 hours removed 12,000 BTU of heat per hour. The name stuck even though modern AC uses refrigerant, not ice.
Common residential AC sizes in tons: 1.5, 2, 2.5, 3, 3.5, 4, 5. Most single-family homes need 2 to 4 tons. Window units and small ductless mini-splits are often rated in BTU/hr rather than tons.
An undersized AC runs continuously on a hot day without ever reaching your set temperature. Your house stays warm, your electricity bill climbs, and the compressor wears out faster from constant use. On a 100-degree day in Phoenix, a 2-ton AC in a 2500 sqft house is going to lose the battle by afternoon.
An oversized AC is actually a more common problem than undersizing. A unit that is too large for your home reaches the set temperature fast, shuts off, then kicks back on again 10 minutes later. This is called short-cycling. The issue is that AC pulls humidity from your air during the cooling process, but that process needs time. When the unit short-cycles, your home stays at the right temperature but feels clammy and sticky because the moisture never gets removed. Short-cycling also hammers the compressor with repeated starts and shortens equipment life.
HVAC contractors size for the "design day": the hottest outdoor temperature your area hits in a typical year (usually the 99th percentile temperature from weather data). A properly sized AC should run about 80-90 percent of that design day to maintain your indoor set temperature. That means it runs a long time, but it does cycle off. If it runs 100 percent of the time and still can't keep up, it is undersized. If it cycles off every 10-15 minutes on a design day, it is oversized.
The biggest factor. The standard starting point is 20 BTU per square foot of living space. A 1500 sqft home starts at 30,000 BTU = 2.5 tons. A 2000 sqft home starts at 40,000 BTU = 3.3 tons (rounds to 3.5).
This is the second-biggest variable. A home in Phoenix hits 115 degrees and needs to maintain a 50-degree indoor-to-outdoor temperature difference. The same home in Minneapolis might only need to handle a 90-degree day. That difference matters a lot for sizing. Hot climates need 15-20 percent more cooling capacity than mixed climates. Cold climates need 10-15 percent less cooling capacity (though they need much more heating capacity, which is a separate calculation).
A drafty older home with single-pane windows leaks cooled air out and lets hot air in much faster than a modern home built to the 2012 International Energy Conservation Code (IECC). That can swing your AC requirement by 15-20 percent in either direction. If you have an older home and you've added blown-in insulation or replaced windows, you may land between the "poor" and "average" categories.
People generate heat. Each person adds roughly 250-400 BTU/hr of sensible heat to a space at rest (more when active). Bedrooms are a good proxy for household size. Three bedrooms and under is a baseline; each extra bedroom adds about 1500 BTU/hr to the load, which is roughly another person's heat output plus electronics.
This is a simplified calculator designed to give you a reliable starting point. Before buying equipment, you should know it does not account for:
For a calculation that accounts for all these variables, that is a full ACCA Manual J load calculation. Your HVAC contractor runs one before sizing your system. You can also use our HVAC Load Sizing Calculator which includes climate zone, window load, and door load.
Most 1500 square foot homes in a mixed climate (states like Kentucky, North Carolina, or coastal California) need a 2.5 ton air conditioner. The range is 2 to 3 tons depending on your insulation quality, how many people live in the home, and how hot your local summers get. In a very hot climate like Florida or Texas, you may need 3 tons. In a colder climate like Minnesota or Wisconsin, 2 tons may be enough.
A 1000 square foot home typically needs a 1.5 to 2 ton air conditioner. In a hot climate like Florida, Arizona, or Texas, a 2 ton unit is more appropriate. In a cooler northern climate, 1.5 tons is usually sufficient. The standard rule of thumb is 20 BTU per square foot of living space, adjusted for climate and insulation.
A 1400 square foot home in an average climate needs about a 2 to 2.5 ton air conditioner. In a hot climate, 2.5 tons is the better choice. In a well-insulated newer home in a cool climate, 1.5 tons may be sufficient. Use the calculator above with your specific square footage, climate, and insulation to get a more precise recommendation.
A 'ton' measures an air conditioner's cooling capacity. It has nothing to do with weight. One ton equals 12,000 BTU per hour of heat removed. A 2.5 ton AC removes 30,000 BTU of heat from your home each hour it runs. Residential AC units typically come in 1.5, 2, 2.5, 3, 3.5, 4, and 5 ton sizes. Getting the right size matters: too small means it runs constantly and can't keep up on hot days; too big means it short-cycles and leaves your home feeling humid.
Yes, an oversized AC is a real problem. When an AC is too large for your home, it reaches the set temperature too fast, shuts off, and then kicks back on again shortly after. This is called short-cycling. Short-cycling makes your home feel clammy and humid because the AC does not run long enough to pull moisture from the air. It also wears out the compressor faster from all the starts and stops. The goal is a unit sized so it runs for most of a hot day without constant cycling.
This calculator uses a simplified version of the ACCA Manual J method, which is the industry standard for residential AC sizing. It may help you narrow your search to a size range before talking to an HVAC contractor. It does not replace a full Manual J calculation, which also accounts for ceiling height, duct condition, window count and direction, and local design temperatures. Use this for a starting point, then confirm with a licensed contractor before purchasing equipment.