Method: Preliminary envelope and solar load is calculated as: Q_envelope = Floor Area × Envelope Load Factor Occupancy load is: Q_people = Number of People × Heat Gain per Person Lighting and equipment loads are added directly after conversion to watts. Outdoor-air sensible cooling load is estimated from: Q_air = ρ × c_p × V̇ × ΔT using an air density of approximately 1.2 kg/m³ and specific heat capacity of approximately 1.006 kJ/kg·K. Base Cooling Load = Envelope + Occupancy + Lighting + Equipment + Outdoor-Air Sensible Load Final Cooling Load = Base Cooling Load × (1 + Design Margin) Refrigeration capacity is converted using: 1 TR ≈ 3.51685 kW and: 1 kW ≈ 3412.14 BTU/h This is a preliminary sizing calculator, not a full HVAC heat-balance calculation. The envelope-and-solar input is intentionally editable because actual heat gain depends on wall and roof construction, glazing, orientation, shading, climate and solar exposure. The outdoor-air calculation accounts only for sensible temperature load. Humidity and latent ventilation load can be significant in humid climates and should be included in detailed HVAC design. Final equipment selection should consider detailed envelope properties, glazing solar gain, ventilation requirements, latent loads, diversity, occupancy schedules, duct heat gain, fan heat and applicable HVAC design standards.