Mini Split Sizing Chart (BTU by Room Size)
A quick-reference mini-split sizing chart — match your room’s square footage to the BTU capacity and the standard unit size (9k, 12k, 18k, 24k, 36k) it points to.
Prices vary by location. Verify with local suppliers.
Mini-split sizing chart (BTU by room size)
Match your room’s square footage to a standard mini-split size. The chart assumes 8-ft ceilings, average insulation and a mild-to-mixed climate — the calculator above adjusts these for your actual room, which is what a bare chart can’t do.
| Room size (sq ft) | BTU | Tonnage | Typical use |
|---|---|---|---|
| 350–450 | 9,000 | ¾ ton | Bedroom, office, nursery |
| 450–600 | 12,000 | 1 ton | Large bedroom, living room, studio |
| 600–1,000 | 18,000 | 1.5 ton | Great room, 2-car garage, open area |
| 1,000–1,400 | 24,000 | 2 ton | Open main floor, small home, ADU |
| 1,400–1,800 | 36,000 | 3 ton | Large open floor, small whole home |
Adjust the chart for your room
- Climate: hot southern and very cold northern climates push you up a row.
- Ceilings: 9-ft, 10-ft or vaulted ceilings add ~10–30% capacity.
- Sun & insulation: a sunny, top-floor or poorly insulated room adds capacity; shade and good insulation subtract it.
- Kitchens & people: add ~4,000 BTU for a kitchen and ~600 BTU per occupant beyond two.
Every figure is a planning estimate; an HVAC pro confirms it with a Manual-J load calculation. For a whole home, use a multi-zone system and size it to the combined load — set the calculator to 2–4 zones. Jump to a size: 9k · 12k · 18k · 24k · 36k.
Frequently asked questions
What size mini split do I need for my square footage?
As a quick chart: 9,000 BTU covers about 350–450 sq ft, 12,000 BTU about 450–600 sq ft, 18,000 BTU about 600–1,000 sq ft, 24,000 BTU about 1,000–1,400 sq ft, and 36,000 BTU about 1,400–1,800 sq ft. These assume 8-ft ceilings and average insulation in a mild-to-mixed climate; hotter climates, tall ceilings, strong sun or poor insulation bump you up a row.
How many tons is a 12,000, 24,000 or 36,000 BTU mini split?
Capacity converts at 12,000 BTU per ton: 12,000 BTU = 1 ton, 18,000 BTU = 1.5 tons, 24,000 BTU = 2 tons, and 36,000 BTU = 3 tons (9,000 BTU is ¾ ton). The common US single-zone sizes are 9k, 12k, 18k, 24k and 36k BTU.
Do sizing charts account for ceiling height?
No — a standard chart assumes 8-foot ceilings. A 9-, 10-foot or vaulted ceiling means noticeably more air to condition, so you add roughly 10–30% capacity above the chart value for that room. The calculator on this page applies the ceiling adjustment for you.
Should I round up or down when between two sizes?
Round up to the next standard size — that rounding is the built-in safety margin, and it’s why you should not then deliberately oversize on top of it. Because inverter mini-splits modulate their output, a right-sized unit runs longer at low speed and controls humidity better; a genuinely oversized one short-cycles. For borderline cases, confirm with a Manual-J load calculation.