Rule-of-thumb estimates only — not a substitute for a Manual J or block load calculation. Use for early feasibility and equipment pre-selection.
| Building Type | SF / Ton | CFM / SF | Heat (BTU/SF) |
|---|---|---|---|
| Office | 300–400 | 0.8–1.2 | 25–40 |
| Retail | 200–300 | 1.0–1.5 | 30–50 |
| Restaurant | 100–200 | 1.5–2.5 | 50–80 |
| School | 250–350 | 1.0–1.5 | 30–50 |
| Medical Office | 200–300 | 1.0–1.8 | 35–55 |
| Warehouse | 500–800 | 0.3–0.6 | 10–20 |
| Hotel | 350–500 | 0.7–1.0 | 20–35 |
| Residential | 400–600 | 0.5–0.8 | 20–35 |
| Server / Data | 50–150 | 2.0–5.0 | — |
This quick load estimator converts a building’s floor area into approximate cooling tons, heating MBH, and supply CFM using rule-of-thumb factors keyed to building type and climate. Enter the floor area, pick a building type, and select a climate; the tool returns cooling capacity (tons and BTU/hr), heating (MBH), supply airflow, and the implied square-feet-per-ton and CFM-per-square-foot ratios.
It is built for early feasibility, budgeting, and equipment pre-selection — the stage before a full load calculation exists. The factors come from typical commercial practice and shift with climate, but they are deliberately coarse. A detailed Manual J or block load calculation, accounting for envelope, glazing, internal gains, and ventilation, is required for final sizing.
| Cooling tons | Tons = Area (ft²) ÷ (SF-per-ton ÷ climate factor) |
| Cooling BTU/hr | BTU/hr = Tons × 12,000 |
| Supply airflow | CFM = Area (ft²) × CFM-per-ft² |
| Heating load | MBH = Area × (BTU/ft²) × climate factor ÷ 1,000 |
Base factors (square-feet-per-ton, CFM-per-ft², BTU-per-ft²) follow common ASHRAE and industry rule-of-thumb ranges for each building type, then a climate multiplier scales cooling and heating. The constant 12,000 BTU/hr per ton of refrigeration is exact by definition. These are screening estimates, not a substitute for an ASHRAE load calculation.