Commercial HVAC Load Calculator
Rule-of-thumb HVAC sizing using square feet per ton is one of the fastest ways to ballpark cooling capacity for early planning on a commercial building. This calculator takes your building's square footage and building type, then reports the estimated cooling load in both tons and BTU/hr. Building type matters enormously — a restaurant's cooking loads and higher occupancy density drive far more cooling per square foot than a warehouse — so selecting the right type auto-fills an appropriate square-feet-per-ton factor (still editable for custom conditions). For data center-specific cooling load, see the Cooling Load Calculator, and to benchmark an existing building's energy use against national medians, see our Building Energy Benchmark Calculator.
Total conditioned floor area of the commercial building, in square feet.
Selecting a type auto-fills the square feet per ton below (still editable). Factors are ASHRAE / Manual N rule-of-thumb planning values for typical commercial buildings.
Rule-of-thumb cooling load factor: lower means more cooling capacity needed per square foot (denser internal loads). Typical range 175–700 sq ft/ton by building type.
building square footage (sq ft) ÷ square feet per ton
estimated cooling load (tons) × 12,000
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
This rule-of-thumb estimate is for early planning purposes only. A full Manual N or ASHRAE load calculation accounting for building orientation, glazing, insulation, occupancy, and internal loads should always be used for actual equipment sizing, purchasing, or permitting decisions.
How we calculate this →Rule-of-thumb sizing (square feet per ton) is a fast way to right-size HVAC equipment for early planning, but building type changes the answer dramatically: a 20,000 sq ft office needs roughly 57 tons of cooling, while the same square footage as a restaurant -- with its cooking loads and higher occupancy density -- needs closer to 114 tons, double the capacity. These figures are planning-level estimates only; a full Manual N or ASHRAE load calculation should always be used for actual equipment sizing and permitting.
How commercial HVAC cooling load is estimated
This calculator estimates a commercial building's cooling load using rule-of-thumb square-feet-per-ton sizing factors tied to two inputs: the building's floor area and its building type. Two quantities tie the calculation together.
Estimated Cooling Load (Tons) = Building Square Footage (sq ft) ÷ Square Feet per Ton. A "ton" of cooling capacity equals 12,000 BTU/hr — a unit derived from the cooling effect of melting one ton of ice in 24 hours — and the square-feet-per-ton factor is a rule-of-thumb planning value that says how many square feet of a given building type one ton of cooling can typically serve. At 20,000 sq ft and the Office factor of 350 sq ft/ton, that is 20,000 ÷ 350 = 57.14 tons. The factor varies sharply by building type because internal heat gains differ so much: Office 350, Retail 275, Restaurant 175, and Warehouse 700 sq ft/ton — so the same 20,000 sq ft as a restaurant needs 20,000 ÷ 175 = 114.29 tons, roughly double the office, while as a warehouse it needs only 20,000 ÷ 700 = 28.57 tons.
Estimated Cooling Load (BTU/hr) = Estimated Cooling Load (Tons) × 12,000. Since one ton equals 12,000 BTU/hr, multiplying the tonnage by 12,000 converts the result into the BTU/hr figure used in detailed load calculations; at 57.14 tons, that is 57.14 × 12,000 = 685,714 BTU/hr. Both units describe the same cooling capacity — tons are more common when discussing equipment sizing, while BTU/hr is more common in detailed load calculations.
The crucial caveat: this is a rule-of-thumb planning estimate only, not a substitute for a full load calculation. A real Manual N (commercial) or ASHRAE load calculation accounts for climate zone, building orientation, window area and glazing type, insulation levels, infiltration, occupancy, lighting, and internal equipment loads — factors that can meaningfully shift actual required capacity above or below the rule-of-thumb figure. Use this tool for early budgeting and feasibility only; actual equipment purchasing, permitting, and installation should always be based on a detailed load calculation performed by a licensed HVAC engineer or contractor. Data sources: ASHRAE Fundamentals Handbook rule-of-thumb sizing guidance; Manual N (Commercial Load Calculation) methodology from ACCA; building type-specific cooling load factors from ASHRAE 90.1 and commercial HVAC design standards; typical occupancy and equipment loads by building type from commercial energy audits and design guides.