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What Size Mini-Split Do I Need? How to Calculate
Photo: Bartek/ Adobe Stock
Photo: Bartek/ Adobe Stock
Highlights
Mini-split sizes are determined by the number of British Thermal Units (BTUs) required.
You’ll need to measure your room’s square footage first.
To calculate the number of BTUs you need, multiply the square footage by 25.
Your local HVAC professional can help you install a mini-split.
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Picking the right mini-split size is essential for efficiency, comfort, and cost savings. A unit that’s too small won’t cool effectively, while an oversized unit can waste energy and cycle on and off too frequently. To get that perfect level of comfort, you’ll need to do a little math—but don’t worry, no geometry degree is necessary for this project. It all starts with your room's square footage and ends with finding the perfect number of British Thermal Units (BTUs) to keep things cool. Let’s take a deeper dive.
Mini-Split Sizes Based on Square Footage
When it comes to cooling a room, size matters—in this case, it’s all about the square footage. Pick a mini-split unit with too few BTUs, and your system will be working overtime just to keep up. Go too big, and you'll waste energy (and money) faster than you can say “climate control.” The chart below shows the sweet spot for your space—so that comfort isn’t a guessing game.
| Square Footage | Recommended BTUs |
|---|---|
| 100-150 | 5,000-6,000 |
| 150-250 | 6,000-9,000 |
| 250-350 | 9,000-12,000 |
| 350-450 | 12,000-15,000 |
| 450-600 | 15,000-18,000 |
Calculating Mini-Split Sizes
Using your square footage measurements, apply the following formula to determine how many BTUs your mini-split needs:
BTUs = Square Footage x 25
How to Measure Square Footage
Before selecting the perfect mini-split, you’ll need to determine your space’s square footage. Luckily, it’s easier than it sounds: just grab a tape measure, measure the length and width of the room, multiply the two, and there you have it—your square footage.
Length × Width = Square Footage
For oddly shaped rooms, break the space into squares or rectangles, calculate the square footage of each individual shape, and then add them all up.
Who to Hire to Install a Mini-Split
Photo: Tomasz Zajda/ Adobe Stock
Once you do the heavy lifting of determining what size mini-split you need, stop there—now’s the time to hire your local HVAC professional to install the unit for you. Although experienced DIYers can likely handle smaller installations, it’s best to leave this job to an expert who can have your new mini-split up and running in no time. This way, you won’t break a sweat and can instead enjoy the cool reward once the unit’s installed.
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