BTU Calculator
Estimate room BTU for HVAC sizing, convert between energy and power units, and look up appliance heat output ratings. Three tools in one.
Estimate room BTU for HVAC sizing, convert between energy and power units, and look up appliance heat output ratings. Three tools in one.
A British Thermal Unit (BTU) is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. In HVAC, BTU/hr measures the rate of heating or cooling. A typical home might need 30,000-60,000 BTU/hr for heating and 24,000-48,000 BTU/hr (2-4 tons) for cooling.
Square footage is the starting point, but climate zone, insulation quality, window exposure, and occupancy all significantly affect the load. A 200 sq ft room in Phoenix with poor insulation and south-facing windows needs far more cooling than the same room in Portland with good insulation and north exposure.
Every appliance, light, and person in a space adds heat. A kitchen with an oven running can add 5,000+ BTU/hr. A server room with 10 servers might generate 30,000 BTU/hr or more. The Appliances tab shows typical ratings for common equipment to help estimate internal gains.
This calculator provides a simplified BTU estimate for quick sizing. A full ACCA Manual J analysis adds hour-by-hour solar gain modeling, window orientation and shading coefficients, duct losses, latent loads, and ASHRAE design conditions by ZIP code. Use this tool for ballpark estimates — use Manual J for equipment selection.
Was this calculator useful for your project?
Need full Manual J room-by-room load calculations with equipment sizing?