Start with the load question
For equipment labels, use BTU/h: a rate of heat transfer. A room-size estimate can help organize inputs, but it is not a substitute for a design load.
Gather the inputs
- Floor area, ceiling height, and room use
- Insulation, windows, solar exposure, and local design conditions
- People, appliances, ventilation, and humidity where relevant
Make a preliminary estimate
Use the Room BTU Calculator to document a planning value and adjustments. Then express the result as BTU/h, refrigeration tons, or kW only for comparison.
Calculate a capacity conversion
Convert a known BTU/h rating to watts, kilowatts, or refrigeration tons.
Open BTU CalculatorVerify before selection
U.S. DOE guidance warns that rule-of-thumb sizing can oversize comfort systems. Use a recognized load method and qualified professional review for final equipment selection.
FAQ
Can square footage alone size HVAC equipment?
No. It is a preliminary screen only. Building enclosure, climate, humidity, internal gains, and duct or distribution conditions matter.
Is BTU the same as BTU/h?
No. Btu is energy; BTU/h is a rate used to state HVAC capacity.