How to Calculate Btu Calculator
What is Btu Calculator?
BTU (British Thermal Unit) measures the amount of energy needed to raise one pound of water by 1°F. For air conditioning and heating, BTU/hr ratings indicate how much thermal energy a system can move per hour. The right BTU capacity prevents under-cooling (too weak) or short-cycling (too powerful).
Step-by-Step Guide
- 1Start with 20 BTU per square foot of living space
- 2Adjust for ceiling height: multiply by height/8 (standard 8ft ceiling)
- 3Factor in climate zone, sun exposure, and number of occupants
- 4Add 600 BTU per person beyond two regular occupants
Worked Examples
Input
300 sq ft bedroom, 8ft ceiling, moderate climate
Result
6,000 BTU (0.5 ton)
300 × 20 = 6,000 BTU
Input
500 sq ft open plan, 10ft ceilings, sunny
Result
~13,750 BTU (1.1 ton)
Height and sun adjustments add ~37%