Mini-Split Sizing Calculator
BTU class (9/12/18/24k) for a ductless mini-split, with insulation quality factor.
Inverter mini-splits modulate down well, so the next class up is safer than with fixed-speed units — but 2× oversize still ruins dehumidification.
Formula
Mini-Split Sizing Calculator is a free mini split size for HVAC designers, technicians and energy auditors — instant, accurate and 100% client-side, with the governing formula and reference shown next to the result so the number can be defended, not just quoted.
About Mini-Split Sizing Calculator
BTU class (9/12/18/24k) for a ductless mini-split, with insulation quality factor. The calculation implements BTU = area × (500–750 BTU/m² by insulation) × height factor (Manufacturer sizing guides (Daikin/Mitsubishi)). Inverter mini-splits modulate down well, so the next class up is safer than with fixed-speed units — but 2× oversize still ruins dehumidification.
How to use Mini-Split Sizing Calculator
- 1Enter Room area in m².
- 2Enter Insulation quality (1 good · 2 average · 3 poor/leaky).
- 3Enter Ceiling height in m.
- 4Read Required capacity instantly — no submit button needed.
- 5Need US units? Flip the SI/Imperial toggle and every field converts.
Why use Mini-Split Sizing Calculator?
- ✓Implements the standard formula — BTU = area × (500–750 BTU/m² by insulation) × height factor
- ✓Reference cited on-page: Manufacturer sizing guides (Daikin/Mitsubishi)
- ✓One-click SI ⇄ Imperial toggle — values convert in place, physics stays in SI
- ✓Built-in engineering verdict flags out-of-range results instantly
- ✓Runs entirely in your browser — nothing uploaded, free forever
Frequently asked questions
What formula does the Mini-Split Sizing Calculator use?+
It computes BTU = area × (500–750 BTU/m² by insulation) × height factor, per Manufacturer sizing guides (Daikin/Mitsubishi). The formula is displayed under the result.
What should I keep in mind when using this calculator?+
Inverter mini-splits modulate down well, so the next class up is safer than with fixed-speed units — but 2× oversize still ruins dehumidification.
Is this based on ASHRAE methods?+
The calculations follow the standard ASHRAE/ISHRAE formulations cited under the result, simplified where industry practice does the same. For permit-grade design, confirm with the full code procedure.
Is the Mini-Split Sizing Calculator free to use?+
Yes — completely free, no sign-up, no limits. It runs client-side in your browser, so inputs stay private and results are instant even on slow connections.
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