Tons to BTU Calculator

A tons to BTU calculator converts cooling capacity from tons into BTU per hour. One ton of air conditioning is exactly 12,000 BTU/hr, so the calculator multiplies the tonnage by 12,000. A 3 ton central air conditioner is rated at 36,000 BTU/hr. Use it for unit conversion, not for sizing your home.

Last reviewed September 2026Method & sources Report an error

Cooling Capacity

36,000 BTU/hr

Breakdown
Cooling Capacity	36,000 BTU/hr

How to Calculate Tons to BTU

A "ton" of air conditioning capacity is a fixed unit equal to 12,000 BTU/hr. It was originally defined as the cooling power of melting one short ton (2,000 lb) of ice over 24 hours. Multiplying tons by 12,000 gives BTU per hour.

Example: 3 ton central air conditioner

A 3 ton central air conditioner: Cooling capacity: 3 × 12,000 = 36,000 BTU/hr

What Is Tons to BTU?

Central AC and heat pumps are commonly rated in tons. Furnaces and window units are usually rated in BTU/hr. This calculator converts between the two. You can compare capacity figures given in either unit.

Tons to BTU: Pros and Cons

Pros

An exact conversion with no approximation, since a ton is defined as precisely 12,000 BTU/hr
Compares tonnage and BTU ratings directly
Works for any tonnage, including fractions and commercial sizes

Cons

Doesn't tell you what tonnage your home needs. That's a separate load-calculation question, similar to what the Window AC Size and Furnace BTU calculators address for their respective equipment types
A ton of cooling capacity is a nominal rating, not a guarantee of real-world performance. Real-world performance also depends on the specific unit's efficiency and installation conditions

Tons to BTU: What a Pro Checks

Don't assume more tonnage is better. An oversized central air system cools a room quickly but cycles on and off without running long enough to adequately remove humidity. It still feels cold and clammy.
Treat this as a unit conversion only, not a sizing answer. Figuring out the tonnage your home actually needs is a separate load-calculation question. It depends on square footage, climate, and insulation, like what the Window AC Size and Furnace BTU calculators address.

Frequently Asked Questions

How many BTU is a 3 ton AC unit?

36,000 BTU/hr. Multiply the tonnage by 12,000. A 3 ton unit is 3 × 12,000 = 36,000 BTU/hr.

Why is air conditioning capacity measured in tons?

It's a historical unit dating back to when ice was used for cooling. One "ton" of cooling capacity originally referred to the rate of heat absorption needed to melt one short ton (2,000 lb) of ice over 24 hours. That works out to 12,000 BTU/hr.

How do I convert BTU back to tons?

Divide by 12,000. A 24,000 BTU/hr unit is 24,000 ÷ 12,000 = 2 tons.

What size central air unit do I need for my house?

That depends on square footage, climate, insulation, and other factors, much like sizing a window unit. See the Window AC Size calculator's guidance for the general BTU-per-square-foot approach. Keep in mind that whole-house central air sizing benefits from a professional load calculation.

Is a bigger tonnage always better?

No. An oversized central air system, like an oversized window unit, cools quickly but cycles on and off frequently without adequately removing humidity. That leaves a home feeling clammy and wastes energy. Proper sizing matters more than maximum capacity.

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