AC Sizing Calculator

Find the right AC tonnage for your home based on square footage, climate, insulation, and sun exposure.

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🔒 This calculation runs entirely in your browser. Nothing you enter is sent to our servers or stored anywhere.
Recommended size
0 tons
Acceptable range:
Total cooling load0 BTU/h

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See what a unit this size costs installed.

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FAQ

AC Sizing Questions

What size AC unit do I need?

As a rule of thumb, homes need about 1 ton of cooling capacity per 400-600 square feet, adjusted for ceiling height, climate, insulation, and sun exposure. Use the calculator above for an estimate tailored to your home.

What happens if my AC is too big?

An oversized AC cools the air quickly but shuts off before it removes enough humidity, leading to a clammy feel, short-cycling, higher energy bills, and more wear on components.

What happens if my AC is too small?

An undersized AC will run constantly during peak heat and still struggle to reach your set temperature, leading to higher bills and premature wear.

Is this the same as a Manual J load calculation?

No. This calculator uses simplified rule-of-thumb factors for a quick estimate. A licensed contractor performing a full Manual J load calculation will account for windows, orientation, and construction details in far more detail before final equipment sizing.

This calculator provides a rough estimate based on common industry rules of thumb. A licensed HVAC contractor should perform a full load calculation (Manual J) before you purchase equipment.