How Many BTUs for 600 Sq Ft?
600 sq ft is the “Danger Zone.” It sits right between 1 Ton and 1.5 Tons. Choose wrong, and you face humidity issues or high bills. Here is the engineering truth.
The “Rule of Thumb” Range
Insulated Room
12,000 BTU
Garage / Sunroom
18,000 BTU
⚠️ Guessing is expensive. Use the Calculator to be 100% sure.
Why “Square Footage” Lies to You
Most blogs tell you to divide by 600. That is lazy math. A 600 sq ft apartment is NOT the same as a 600 sq ft garage.
Ceiling Height
8ft ceilings = 4,800 cubic ft.
12ft ceilings = 7,200 cubic ft.
That’s 50% more air to cool!
Insulation (R-Value)
Garages have thin doors and concrete floors that suck heat. Read the Garage Guide.
Select Your 600 Sq Ft Scenario
The Apartment / Condo
Shared walls, 8ft ceilings, average insulation.
Open Living / Kitchen
Cooking heat, electronics, multiple people.
When in doubt, use an Inverter.
If your load is 14,000 BTU (awkward size), don’t buy a 12k unit. Buy an 18k Inverter Unit (like Mitsubishi).
Why? An 18k inverter can “ramp down” to run at 6,000 BTUs when the room is cool, preventing short cycling. It gives you the power for hot days and the efficiency for mild days.
See Best 18k Unit ReviewVariable Speed
The Secret to Sizing Safety
Real World: The Basement Project
The 600 Sq Ft “Man Cave”
Scenario: Finished basement, 600 sq ft, 7ft ceilings (low).
The Trap: Online calculator said 18k because of “Square Footage”.
The Reality: Basements are naturally cool (insulated by earth).
Engineering Load: 10,500 BTU
We installed a 12,000 BTU unit. It runs perfectly quietly on low speed.
FAQ: 600 Sq Ft Sizing
Is a 12000 BTU mini split enough for 600 sq ft?
For a standard interior room or apartment with 8ft ceilings: Yes. But if it’s a garage, sunroom, or has poor insulation, 12,000 BTU will struggle on hot days.
Can I use a 24000 BTU unit for 600 sq ft?
Avoid this. A 24k unit is 2 Tons. That is massively oversized for 600 sq ft. It will turn on, blast freezing air for 3 minutes, and turn off (“Short Cycling”). This leaves the room feeling clammy and humid.
How much does it cost to install?
A DIY 12k unit costs around $1,000. A professionally installed 18k unit costs $3,500 – $5,000. Check our Installation Cost Guide.
Stop Guessing. Start Calculating.
Physics doesn’t care about your guess. Get the exact number for your specific room height and window load.
