BTU Calculator

BTU Calculator helps you estimate how much heating or cooling capacity — measured in BTU per hour — a room needs. Enter the room size, set a few details, and get an instant, easy-to-read estimate, completely offline. WHAT YOU CAN DO • Size a room by length × width, or enter the floor area directly • Work in imperial (feet) or metric (meters) units • Adjust for ceiling height, number of occupants, sun exposure and kitchens • See the result in BTU/hr, tons of cooling, and kilowatts • Browse ready-made examples like a bedroom, a sunny living room and a kitchen HOW IT WORKS The estimate uses the common rule of thumb of about 20 BTU per hour per square foot, then adjusts for tall ceilings, strong sun or heavy shade, extra people, and the heat a kitchen adds. It is a fast starting point for choosing an air conditioner or heater. LEARN AS YOU GO A built-in Learn tab explains, in plain language, what a BTU is, what drives the heating and cooling load, and the common pitfalls of over- or under-sizing equipment. IMPORTANT: ESTIMATE ONLY This app provides a rule-of-thumb ESTIMATE for general guidance only. It is not a substitute for a professional Manual J load calculation. Actual requirements depend on insulation, climate zone, windows, air leakage and more. Always confirm equipment sizing with a licensed HVAC technician before you buy. PRIVACY The app works fully offline and collects no personal data — your inputs never leave your device. Ads are served by Google AdMob, which may use an advertising identifier (advertising ID) as described in Google's policies. Light and dark themes, a tiny download, and no clutter. Download BTU Calculator and size your next AC or heater with confidence.