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Cooling Load Calculators

Choosing the right size air conditioner is critical for your comfort and energy efficiency. An oversized unit will short-cycle and fail to remove humidity, while an undersized unit will run constantly and struggle to keep you cool. Use our free tools below to find the perfect fit.

AC Tonnage Calculator

Start here if you are not sure which type of AC you are buying. Works out one room's cooling load in BTU and tons from square footage, climate, ceiling height, sun and insulation, then points you to the right calculator for window, ductless or central.

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AC Tonnage Per Square Foot

Whole-house sizing by square footage: enter your home size and climate to get the recommended central AC tonnage, with a full chart from 600 to 3,500 sq ft.

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Mini Split Size Calculator

Size a ductless mini split by room. Matches your room's cooling load to standard single-zone head capacities from 9,000 to 36,000 BTU, in both BTU and tons, and gives the heating BTU if you will run it as a heat pump.

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Window AC Size Calculator

Find the right window air conditioner BTU for a room. Standard window unit sizes from 5,000 to 24,000 BTU based on your room's cooling load.

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Central AC Size Calculator

Size a central (split-system) air conditioner for your whole house - enter your square footage and climate to get the required tonnage and BTU, with an installed-cost ballpark for the AC, furnace, and both together in the same result.

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Portable AC Size Calculator

Determine the correct BTU rating for a portable air conditioner. Perfect for single rooms, apartments, or supplemental cooling.

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Manufactured & Mobile Home AC Size Calculator

Manufactured-home-specific sizing that accounts for the exposed underbelly and leakier envelope. Gives cooling tonnage plus heat-pump and furnace heating sizes, and flags duct issues before you buy.

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RV AC Size Calculator

Size a rooftop RV air conditioner (11,000 / 13,500 / 15,000 BTU or dual units) from your rig's real heat load, with generator and soft-start power guidance.

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Garage BTU Calculator

Heating and cooling BTU for a garage, sized on the door, insulation and envelope rather than a flat per-square-foot rule. Gives both a heater size and a mini split size.

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Why Use an AC Sizing Calculator?

When it comes to air conditioning, bigger isn't always better. The process of determining the correct AC capacity, measured in BTUs or tons, is called a cooling load calculation.

HVAC professionals use complex manuals (like ACCA Manual J) to perform these calculations, but our tools provide a highly accurate estimate by accounting for essential variables like your local climate zone, home square footage, ceiling height, and insulation quality.

The Dangers of Improper Sizing

  • Oversized AC Units: Cool the house too quickly and shut off before they have a chance to remove humidity from the air, leaving your home feeling clammy and cold. This "short-cycling" also damages the compressor over time.
  • Undersized AC Units: Run non-stop during hot days, driving up your energy bills and wearing out parts prematurely without ever reaching your target thermostat temperature.

Select the calculator above that best matches your needs to get a reliable estimate before you purchase new equipment or request quotes from contractors.