BTU Calculator
Free online BTU calculator for air conditioning and heating. Calculate BTU requirements based on room size, insulation, climate, and occupancy. Determine the right AC or heater capacity in BTU, tons, and kW.
Room Dimensions
What is a BTU Calculator?
A BTU (British Thermal Unit) Calculator is an HVAC tool that helps determine the heating or cooling capacity required for a room or space. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. For air conditioning and heating systems, BTU ratings indicate the capacity to remove or add heat. This calculator considers room size, insulation quality, sun exposure, climate, and occupancy to provide accurate BTU requirements.
Calculation Formula
Basic BTU Formula:
BTU = Room Volume (ft³) × BTU per ft³ × Adjustment Factors
The calculation uses base BTU per cubic foot (typically 3-6 BTU/ft³ for cooling) multiplied by adjustment factors for insulation, sun exposure, and climate. Additional BTU is added for occupants (approximately 600 BTU per person).
Factors Affecting BTU Requirements
- Room size (volume): Larger rooms require more BTU
- Insulation: Poor insulation increases BTU needs by 30%
- Sun exposure: Sunny rooms need 10% more BTU
- Climate: Hot climates require 20% more cooling capacity
- Occupancy: Each person adds about 600 BTU
- Ceiling height: Higher ceilings increase volume and BTU needs
- Window size and quality: Large or single-pane windows increase requirements
- Heat-generating appliances: Kitchen equipment adds heat load
HVAC Sizing Tips
- Don't oversize - larger units cycle on/off more, reducing efficiency
- 1 ton of cooling = 12,000 BTU/hour
- For heating, add 10-15% to the calculated BTU for cold climates
- Consider Energy Star rated equipment for better efficiency
- Split systems may be more efficient than window units for larger rooms
- Regular maintenance improves efficiency and longevity
- Ceiling fans can reduce AC requirements by improving air circulation
- Programmable thermostats can reduce energy consumption by 10-30%
Common Applications
- Selecting appropriate air conditioner size for rooms
- Determining heater capacity for spaces
- HVAC system design and planning
- Energy efficiency assessments
- Home renovation and additions
- Commercial space climate control
- Server room cooling calculations
- Workshop and garage heating/cooling
- Cost estimation for HVAC installation