Every week, somebody hits me with the same question:
“Tony, what mini split size do I need?”
And let me tell you—if you’ve ever gone down the rabbit hole of trying to figure out mini split sizes, you already know the internet is full of charts, calculators, and opinions from people who’ve never installed a system in 100-degree weather while standing on a ladder sweating through their shirt.
So today, I’m cutting through the noise.
This guide is going to walk you through:
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How mini split sizing really works
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Why sizing a ductless unit is totally different from sizing a central AC
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How to pick the right mini split AC sizes for real-world rooms and layouts
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When a mini split is perfect… and when a whole-home system like the Goodman 3-Ton 14.5 SEER2 R32 Bundle makes more sense
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How climate, insulation, and heat load affect your decision
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Mistakes homeowners make all the time
All in plain English — because that’s how I roll.
Let’s talk HVAC like grown adults. No fluff. No glorified marketing talk. Just the truth from Tony Marino.
Mini Split Basics: What You Really Need to Know Before Choosing a Size
Before we talk about individual mini split AC sizes, let’s cover the basics most people overlook.
A mini split is:
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A ductless heat pump or AC
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Designed for targeted, zoned cooling
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Great for additions, garages, sunrooms, bedrooms, and awkward rooms
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More efficient than window units
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More flexible than central air
But here’s the thing—
Mini splits are incredibly sensitive to improper sizing.
Too small, and the unit runs nonstop.
Too big, and it short-cycles, leaving you:
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sticky
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uncomfortable
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and angry at the money you wasted
So yeah—sizing matters.
And it matters way more than with a big central AC system.
The Standard Mini Split Sizes (and What They Actually Mean)
Most mini split outdoor units come in these common sizes:
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6,000 BTU (0.5 ton)
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9,000 BTU (0.75 ton)
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12,000 BTU (1 ton)
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18,000 BTU (1.5 ton)
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24,000 BTU (2 ton)
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30,000 BTU (2.5 ton)
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36,000 BTU (3 ton)
These “sizes” refer to the system’s cooling output.
But that doesn’t mean:
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a 12,000 BTU unit cools exactly 500 sq ft
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or a 24,000 BTU unit cools exactly 1,000 sq ft
That’s amateur math.
Mini split sizing is about heat load, not square footage alone.
Heat load depends on:
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climate
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sun exposure
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insulation
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ceiling height
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number of windows
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room usage
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air leakage
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humidity
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how many people use the space
That’s why the “BTU per square foot” charts online are misleading.
Rule of Thumb for Mini Split Sizes (But With a Big Tony-Style Warning)
Here’s the rough guideline most pros start with:
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6,000 BTU: up to ~250 sq ft
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9,000 BTU: 250–450 sq ft
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12,000 BTU: 450–650 sq ft
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18,000 BTU: 650–900 sq ft
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24,000 BTU: 900–1,200 sq ft
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30,000 BTU: 1,200–1,500 sq ft
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36,000 BTU: 1,500–1,800 sq ft
But again—
This is only a starting point.
A poorly insulated 350-sq-ft garage with west-facing windows?
You might need an 18,000 BTU.
A super-tight, well-insulated bedroom in a shaded home?
A 9,000 BTU might be overkill.
Real sizing requires more than just a quick glance at a chart.
Why People Overcomplicate Mini Split Sizing
Let me tell you the truth:
Mini split sizing is confusing because the industry makes it confusing.
Some brands want you to buy bigger units (bigger profit).
Some want to sell you multi-zone systems you don’t need.
Some online calculators treat every room like a perfect insulated cube floating in outer space.
But your home isn’t a cube.
Your home is a messy, complicated heat trap.
For example:
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Kitchens get hotter because appliances pump heat into the room.
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Additions usually leak air like crazy.
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Bonus rooms above garages get cooked in summer.
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Sunrooms are basically greenhouses with couches.
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Basements stay chilly and need much less BTU.
So yeah—the “one-size-fits-all” approach doesn’t work.
Mini Split Sizes by Room Type (The Real-World Tony Marino Version)
Now we get into the practical stuff.
Here’s what I've seen over 20+ years on the job.
1. Bedrooms
Size needed: 6,000–9,000 BTU
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Typically well-insulated
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Low heat load
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Usually one exterior wall
2. Living Rooms
Size needed: 12,000–18,000 BTU
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Larger spaces
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More windows
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Higher occupancy
3. Kitchens
Size needed: 12,000–18,000 BTU (minimum)
Kitchens always need more cooling—appliances + people + humidity.
4. Garages
Size needed: 18,000–24,000 BTU
Garages are hot boxes with poor insulation unless upgraded.
5. Sunrooms
Size needed: 18,000–36,000 BTU
Sunrooms are the “boss level” of HVAC challenges.
6. Finished Basements
Size needed: 6,000–12,000 BTU
Basements stay cooler, so they need less BTU than expected.
7. Bonus Rooms Over Garage
Size needed: 12,000–18,000 BTU
These rooms get hotter than the rest of the house.
When a Mini Split Isn’t the Best Choice
Listen—I love mini splits.
They’re efficient, flexible, and solve problems central AC can’t.
But they’re not always the right solution.
A mini split might not be a good idea if:
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You want even cooling across the whole home
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You don’t want multiple wall-mounted heads
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You plan to sell soon and want traditional appeal
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You need strong heating in extreme cold
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You’re replacing an aging central AC
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You dislike the look of air handlers on the wall
Sometimes, the right answer is to upgrade the whole system—
and that’s where the Goodman 3-Ton 14.5 SEER2 R32 Bundle comes into play.
Why Some People End Up Choosing a Full 3-Ton System Instead of Mini Splits
Let’s be blunt:
Homeowners often start researching mini split AC sizes, get overwhelmed, and eventually realize they actually need a whole-home system upgrade.
Here’s why:
1. Mini splits multiply
One for the bedroom.
One for the living room.
One for the office.
One for the kitchen.
Suddenly you’re buying 4 units instead of 1.
2. Multi-zone mini splits lose efficiency
Each zone steals BTUs from the other.
Your “3-ton” multi-zone system might deliver far less cooling to each room.
3. A 3-ton central AC is often cheaper
A full Goodman system often costs less than multiple mini splits.
4. Home resale value
Buyers still expect central AC in most areas.
5. Ductwork already exists
If your ducts are in good shape, why reinvent the wheel?
And that leads us to the system you originally came here for…
Where the Goodman 3-Ton R32 Bundle Fits Into the Conversation
You might be wondering:
“Tony, what does a 3-ton central AC have to do with mini split sizes?”
Here’s the answer:
A lot of people researching mini split sizing aren’t cooling a single room — they’re trying to fix their entire home’s cooling problems.
A 3-ton system like the Goodman 3-Ton 14.5 SEER2 R32 Bundle is perfect for:
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1,400–1,800 sq ft homes
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Houses with existing ductwork
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Folks replacing tired R22 or R410A systems
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Anyone wanting long-term reliability
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Homes with consistent room-to-room temperatures
And the R32 refrigerant?
Cleaner. More efficient. More future-proof.
You get:
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A matched condenser + air handler
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Strong cooling performance
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Better humidity control
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Lower environmental impact
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Long-term parts availability
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Solid durability without the premium price tag
It’s just a smart upgrade for homeowners who want simplicity and performance.
Some Helpful Resources
Here are four homeowner-friendly resources that actually matter — not fluff.
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For understanding home cooling and HVAC efficiency, see Energy.gov’s guide to AC systems:
Home cooling basics -
ASHRAE’s fundamentals for proper HVAC sizing — the industry’s official gold standard:
ASHRAE technical resources -
ENERGY STAR’s guidance on reducing heat load through proper insulation:
Seal & insulate details -
EPA’s breakdown of modern refrigerants including R32:
Refrigerant transition info
Those four are the only ones you need. The rest is noise.
Final Word From Tony Marino
Mini splits are fantastic — when they’re sized right.
But sizing is a game of inches, not guesses.
Mini split sizes vary wildly based on:
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climate
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insulation
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room type
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sun exposure
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window count
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airflow
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building materials
Get it wrong, and you’ll feel it every month on your electric bill.
Get it right, and mini splits are some of the most efficient cooling systems on the market.
But don’t forget:
For whole-home cooling, sometimes the smartest move isn’t five mini splits…
It’s one well-sized central system like the Goodman 3-Ton 14.5 SEER2 R32 Bundle.
If you want comfort, reliability, and a simple setup that works for years, Goodman delivers every time.
And if you’re still unsure what size you need — ask me.
I’ve seen every mistake in the book, and you don’t need to repeat any of them.
