Mini-splits come in fixed head sizes — 9,000 / 12,000 / 18,000 / 24,000 / 36,000 BTU. Add each room as a zone: we snap every room to the right head, total the connected load, and suggest the multi-zone condenser range in BTU and tons. Share the plan with a link.
Climate and defaults follow the US/India switch in the header. The share link encodes your zones in the URL — nothing is uploaded. Estimate only; confirm with an installer's load calculation.
| Connected head total | — |
| Calculated load total | — |
| Suggested condenser | — |
Unlike central AC, a mini-split is sized room by room, then the rooms are matched to one outdoor condenser:
Because rooms rarely peak together, a multi-zone condenser is usually rated at 70–100% of the connected head total (makers publish allowed connection ratios up to ~130%). Example: three heads of 9k + 9k + 12k = 30k connected typically pair with a 24k–30k condenser. Don’t oversize the condenser — at low load an oversized inverter dehumidifies poorly.
Inverter mini-splits modulate down, so mild oversizing is more forgiving than with single-stage central AC — but going more than one zone size up still hurts dehumidification and efficiency at low load.
Not necessarily. Because all rooms rarely peak at once, multi-zone condensers are commonly rated at 70–100% of the connected head total (manufacturers publish allowed connection ratios up to 130%). A 9k+9k+12k head set (30k connected) typically pairs with a 24k–30k condenser.
Standard indoor head sizes are 9,000, 12,000, 18,000, 24,000 and 36,000 BTU/hr. Each room's load is snapped to the right head, and very small rooms still take the 9k minimum.
Slightly less. A one-to-one (single-zone) system is the most efficient and holds capacity best; a multi-zone condenser serving several heads carries some penalty and can struggle at very low loads if oversized. Match the condenser to the connected head total (commonly 70–100% of it) rather than over-buying.
Most modern mini-splits are heat pumps, so the same system heats in winter by running in reverse. Cold-climate models hold useful output well below freezing. Size on the cooling load first, then check the heating capacity at your winter design temperature — see heat pump sizing basics.
head loads use ACCA Manual J factors; equipment ratings per AHRI 210/240 — ACCA, AHRI. See our full methodology.