Mini-Split BTU Sizing Calculator

Enter your room; get the BTU class to actually buy — computed straight from the public ENERGY STAR sizing chart, not a made-up “20 BTU per sq ft” multiplier. Then see real models whose specs each trace to a manufacturer page. verified 2026-06-10  No signup. Runs entirely in your browser.

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Which zone am I in?
  • Zone 1: South Florida, Hawaii, Puerto Rico
  • Zone 2: Most of Florida, south Texas, southern Louisiana, Phoenix area
  • Zone 3: Most of the Southeast, central Texas, southern California
  • Zone 4: Virginia, Kentucky, Missouri, Kansas, coastal Oregon/Washington
  • Zone 5: Pennsylvania, Ohio, Illinois, Iowa, Colorado, southern New England
  • Zone 6: Minnesota, Wisconsin, Montana, Vermont, New Hampshire, most of Maine
  • Zone 7: North Dakota, northern Minnesota, high Rockies
  • Zone 8: Interior and northern Alaska

State examples are approximate — zones are assigned by county. Use the DOE lookup for your county. DOE county lookup ↗

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FAQ

What size mini split do I need for 500 sq ft?

Per the ENERGY STAR sizing chart, a 450–550 sq ft room needs about 12,000 BTU/h of cooling — a 12,000 BTU (1-ton) mini split. Very sunny rooms need ~10% more; heavily shaded rooms ~10% less. See the 500 sq ft guide.

How many BTU per square foot for a mini split?

The ENERGY STAR chart works out to roughly 20–34 BTU per sq ft depending on room size — smaller rooms need more BTU per sq ft than large ones, so a flat 20 BTU/sq ft rule oversizes large rooms and undersizes small ones. Use the chart bands (this calculator does) instead of one multiplier.

Is it better to oversize a mini split?

No. An oversized inverter unit short-cycles, dehumidifies poorly and wears faster. Match the size class to the calculated load; only size up when heating in a cold climate is the primary job.

Can a mini split heat my home in winter?

Depends on the model's minimum operating temperature: standard units in this dataset are rated to 5°F or −13°F, and the cold-climate Senville AURA runs to −22°F. In DOE zones 5+ pick a low-temperature-rated unit and verify heating capacity at your design temperature with an installer.

All outputs are estimates for shortlisting equipment — not an ACCA Manual J load calculation and not professional advice. Confirm with a licensed installer. How the math works →