How It Works
Mini split sizing uses the same 20–25 BTU per square foot rule as other AC sizing, adjusted for ceiling height, sun exposure, and occupants. The result is rounded up to a standard unit size — 9k, 12k, 18k, 24k, 36k, or 48k BTU.
Calculation Explanation
Example: 800 sq ft with normal sun and 2 people → 800 × 20 = 16,000 BTU, rounded to an 18,000 BTU (1.5 ton) unit — the standard size for a large living area or small apartment.
For whole-house setups, add your room sizes together and use the AC Tonnage Calculator to cross-check, or the BTU Calculator for precise single-room sizing.
Mini Split Size Quick Reference
| Mini Split Size | BTU | Typical Coverage |
|---|---|---|
| 9k (0.75 ton) | 9,000 | 300–450 sq ft |
| 12k (1 ton) | 12,000 | 450–600 sq ft |
| 18k (1.5 ton) | 18,000 | 600–900 sq ft |
| 24k (2 ton) | 24,000 | 900–1,200 sq ft |
| 36k (3 ton) | 36,000 | 1,200–1,800 sq ft |
| 48k (4 ton) | 48,000 | 1,800–2,400 sq ft |