A BTU (British Thermal Unit) calculator determines the air conditioning or heating capacity needed for a room based on its square footage, ceiling height, and insulation quality.
About this calculator
A BTU (British Thermal Unit) calculator determines the air conditioning or heating capacity needed for a room based on its square footage, ceiling height, and insulation quality. Choosing the right BTU capacity ensures efficient climate control without wasting energy.
An undersized AC struggles to cool the room; an oversized one cycles on and off too frequently without properly dehumidifying. BTU calculations help you buy the right-sized unit for your space.
Common uses
- Determine the required BTU for an air conditioner in a bedroom
- Size a heater for a living room in a cold climate
- Select the right HVAC unit for a commercial space
- Calculate BTU for multiple zones in a large home
Frequently asked questions
How many BTU do I need per square foot?
A general rule: 20–25 BTU per square foot for cooling. A 200 sq ft room needs 4,000–5,000 BTU, which corresponds to a 1 tonne (12,000 BTU) AC running part-time. Adjust upward for: south-facing rooms, high ceilings, poor insulation, many windows, or heat-generating equipment.
What is the relationship between BTU and tonnes in AC ratings?
In India, AC capacity is often measured in tonnes of refrigeration. 1 tonne = 12,000 BTU/hour. A 1.5 tonne AC = 18,000 BTU/hour. This is generally suitable for rooms of 150–250 sq ft with average ceiling height and insulation.