AC Tonnage Size Calculator

Use this free AC tonnage calculator to estimate the right system size for your home based on square footage, climate zone, and system type.

Calculate your required system size:

1. Zone / Region

Select the region you live in according to the color keyed map

2. System Type

Select the system type needed for your home

3. Heating Type

Select the optional heating type

4. Room Size

Enter the approximate square feet of the area in your home that you need to heat/cool — min. 600 Sq.ft

Room size less than 400 sq. ft.? See Mini Splits

You’ll see recommended AC Systems based on this calculation.

*This calculator is not intended for use in sizing mobile home systems.

Enter your zone, system type and room size above to see recommended systems

or browse all systems

System Size

Zone 1

Zone 2

Zone 3

Zone 4

Zone 5

1.5 Ton

600 - 900 sf

600 - 950 sf

600 - 1000 sf

700 - 1050 sf

700 - 1100 sf

2 Ton

901 - 1200 sf

951 - 1250 sf

1001 - 1300 sf

1051 - 1350 sf

1101 - 1400 sf

2.5 Ton

1201 - 1500 sf

1251 - 1550 sf

1301 - 1600 sf

1351 - 1600 sf

1401 - 1650 sf

3 Ton

1501 - 1800 sf

1501 - 1850 sf

1601 - 1900 sf

1601 - 2000 sf

1651 - 2100 sf

3.5 Ton

1801 - 2100 sf

1851 - 2150 sf

1901 - 2200 sf

2001 - 2250 sf

2101 - 2300 sf

4 Ton

2101 - 2400 sf

2151 - 2500 sf

2201 - 2600 sf

2251 - 2700 sf

2301 - 2700 sf

5 Ton

2401 - 3000 sf

2501 - 3100 sf

2601 - 3200 sf

2751 - 3300 sf

2701 - 3300 sf

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Residential Load Calculation

We also offer a professional load calculation based on your floor plan, location, and all variables. The turnaround for this service is 1-2 days.

Learn More

Proper System Sizing

Overall Guidance and Conversion

The most accurate method for scientifically determining the right air conditioner size is a Residential Load Calculation.

Our AC tonnage calculator uses similar principles for a reliable online estimate.

When you need to find the size of your system, you can look at the model number on the outdoor unit. The model number includes the tonnage capacity encoded in the numbers. A manual calculator can convert BTUs to tons.

For example, model GSX140241K is a 2-ton unit. Why? There are 12,000 BTUs per ton. The number 24 in the model number indicates the unit is 24,000 BTUs. When you divide that by 12,000 BTUs per ton, it equals 2 tons.

24,000 BTUs/12,000 BTUs per ton = 2 tons

Use the following conversion information to determine your existing system size (use the system model number, NOT the serial number):

18 = 1.5 tons

24 = 2 tons

30 = 2.5 tons

36 = 3 tons

42 = 3.5 tons

48 = 4 tons

60 = 5 tons

When using any HVAC size Calculator, be careful not to make the mistake of getting a too large unit. If the system you install is too large for the space, it will short-cycle (turn on and off frequently). This will not allow the unit to properly dehumidify the space which can cause moisture issues, mold growth, and other problems. It also causes the system to wear out prematurely and use more energy.

Heating Square Footage Range by Climate Zone

30 – 35 BTU's per square foot

35 – 40 BTU's per square foot

40 – 45 BTU's per square foot

45 – 50 BTU's per square foot

50 – 60 BTU's per square foot

Heating Guide & HVAC Size Calculator

Heating load and cooling load are calculated differently. In northern climate zones (4 and 5), size the heating system first using the BTU-per-square-foot ranges above, then confirm cooling capacity with the tonnage table. Our AC tonnage calculator above provides a cooling estimate; for whole-home heating and cooling balance, request a professional Manual J load calculation.

Insulation Variables

Insulation quality significantly affects tonnage requirements. Well-insulated homes (R-38+ attic, sealed ducts) may need 5–10% less capacity than the baseline. Poorly insulated or drafty homes may need 10–15% more. Window area, ceiling height, and air infiltration also shift the result — use the calculator inputs above to account for your home's specific conditions.