Uses the same engine as the full calculator (occupants 2, one large window assumed).
| Cooling load | — |
Common 400 sq ft dimensions: 20×20 ft, 16×25 ft, 10×40 ft. If you searched for one of these room sizes, this is your page — the load math depends on area, not shape.
US (whole home, central system): at the moderate-climate rate of ~22 BTU per sq ft, 400 sq ft works out to 8,800 BTU/hr, i.e. a 1.5 ton unit. Your climate zone shifts this substantially:
| US climate zone | Cooling load | Central AC size |
|---|---|---|
| Zone 1 — Hot (FL, S.TX, AZ desert) | 11,200 BTU/hr | 1.5 ton |
| Zone 2 — Warm (Deep South, TX) | 10,000 BTU/hr | 1.5 ton |
| Zone 3 — Moderate (TN, NC, MO) | 8,800 BTU/hr | 1.5 ton |
| Zone 4 — Mild (Mid-Atlantic, PNW) | 8,000 BTU/hr | 1.5 ton |
| Zone 5 — Cool (Upper Midwest, New England) | 7,200 BTU/hr | 1.5 ton |
India (single room, split AC): at hot-climate loads (~100 BTU/sq ft once ceiling and sun factors apply), a 400 sq ft room needs about 36,800 BTU/hr → a multiple split units (room-by-room). Top floor under an RCC roof, or big west-facing windows? Step up half a ton or pick a high-ISEER model.
These figures assume 8 ft ceilings (9.5 ft for India), average insulation and normal sun. Your real number can swing ±30% — run the full tonnage calculator with your actual room data, including ceiling height, sun exposure and occupancy.
0.75 ton 1 ton 1.5 ton 2 ton 2.5 ton 3 ton 3.5 ton 4 ton 5 ton
About 8,800 BTU/hr for a 400 sq ft US home in a moderate climate (22 BTU/sq ft), rising to 11,200 BTU/hr in hot Zone 1 climates. A single hot Indian room of this size needs roughly 36,800 BTU/hr.
In a moderate US climate with average insulation, a 400 sq ft home carries roughly 8,800 BTU/hr of cooling load, which calls for a 1.5 ton system. Hot climates (Zone 1–2) push the load 15–25% higher; cool climates pull it lower.
A single 400 sq ft room in hot Indian conditions typically needs about 36,800 BTU/hr — a multiple split units (room-by-room). Add roughly 10–15% for top-floor rooms under an RCC roof or strong west-facing sun.
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How these figures are derived: BTU per square foot, honestly · refine for your exact room with the full tonnage calculator.