HVAC Cooling Load Calculator
Estimate peak room cooling load for early AC sizing. Accounts for room dimensions, Gulf design conditions (46 °C / 24 °C), orientation, glazing SHGC, occupancy, equipment and outdoor air (sensible and latent).
Top floor room under a sun-exposed roof
75 W sensible + 55 W latent per person, plus 2.5 L/s outdoor air
Computers, appliances and lighting (all as sensible heat)
Cooling Load
3.5 kW
Tonnage
1.0 TR
BTU/hr
12k
11,899 BTU/hr
Recommended AC Unit
1 Ton (12,000 BTU)
Includes 10% safety factor
Notes:
- 1 Ton of Refrigeration = 12,000 BTU/hr = 3.517 kW
- Safety factor of 10% included for peak loads
- Simplified peak method: one external wall (room length × height), glazing solar gain from SHGC, outdoor air at ASHRAE 62.1 office rates
- Gulf zones use 46 °C outdoor / 24 °C indoor, the Dubai Municipality design convention
- Indicative only: a full hourly load calculation is needed for final design
- Consider additional capacity for kitchen areas
- Consult HVAC engineer for precise system design
DISCLAIMER
This calculator provides ESTIMATES for preliminary planning purposes. Results are based on standard assumptions and may not reflect your specific project conditions.
By using this tool, you acknowledge that:
1. All calculations are approximate and based on typical industry standards and assumptions.
About This Calculator
The HVAC Cooling Load Calculator helps MEP engineers and contractors size air conditioning systems for buildings across the UAE and Gulf. It estimates the peak room load from conduction through the external wall, glazing and roof, solar gain through glazing (using the glass SHGC), sensible and latent heat from people and equipment, and outdoor air and infiltration. Gulf zones use the 46 °C dry-bulb / 24 °C indoor design convention used by Dubai Municipality. It is a simplified method for early sizing, not a replacement for a full hourly load calculation.
When to Use This Calculator
- Sizing air conditioning systems for new buildings
- Selecting AC tonnage for residential villas
- Checking room-by-room loads before a central system design
- Verifying HVAC consultant's load calculations
- Estimating cooling costs for project budgets
How to Use This Calculator
Enter Room Dimensions
Input room length, width, and height to establish the space volume.
Define Envelope
Enter the window area and glazing type (U-value and SHGC), the insulation level, the orientation of the main window, and whether the room is under the roof.
Set Climate Zone
Select the climate zone. Gulf zones use 46 °C outdoor and 24 °C indoor design temperatures.
Add Internal Loads
Enter the number of occupants and the equipment and lighting watts. Outdoor air is added at 2.5 L/s per person plus 0.3 L/s per m².
Review Results
Get total cooling load in BTU/hr, kW, and TR (tons of refrigeration).
Typical Scenarios in UAE & Gulf Projects
A 10 m × 5 m living room (3 m high) with 6 m² of double low-E glazing (SHGC 0.35) facing west, standard insulation, 6 occupants and 800 W of equipment and lighting. At 46 °C / 24 °C the calculator gives 6.09 kW (1.73 TR, about 122 W/m²), including 10% safety factor, and recommends a 2 TR unit. If the room is on the top floor under the roof, the load rises to 6.78 kW (1.93 TR, about 136 W/m²).
A 5 m × 4 m west-facing bedroom with 3 m² of glazing, 2 occupants and 300 W of equipment. With clear double glazing (SHGC 0.70) the load is 3.22 kW (0.92 TR, about 161 W/m²); switching to double low-E glass (SHGC 0.35) cuts it to 2.50 kW (0.71 TR, about 125 W/m²). Solar gain through west glass is the largest single component, so glazing choice matters more than room size.
Frequently Asked Questions
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Last Updated: January 2026
Standards Reference: Simplified method based on ASHRAE Handbook of Fundamentals load components and ASHRAE 62.1 outdoor air rates; 46 °C outdoor design per Dubai Municipality convention. Indicative only.