Why use this calculator
Sizing your HVAC system correctly ensures comfort and energy efficiency. Undersized units can't keep up; oversized units cycle on and off wastefully.
How to use it
Enter room dimensions and insulation quality. The calculator estimates the BTU capacity needed for cooling.
The formula
Base BTU = Square Footage × 25 BTU/sqft, adjusted for insulation quality. 1 ton of cooling = 12,000 BTU.
Worked examples
15×12 room, 8ft ceiling, average insulation
4,500 BTU needed, 0.38 tons
When people use it
- AC unit selection
- Furnace sizing
- HVAC system design
- Room-by-room climate planning
Tips
- Sunny rooms may need 10% more BTU
- Kitchens typically need an extra 4,000 BTU
- Consider window count and direction in your assessment
Questions people ask
- What is a BTU?
- A British Thermal Unit is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. In HVAC, it measures heating/cooling capacity.