HVAC Load Estimator
Rough heating/cooling load.
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About HVAC Load Estimator
The HVAC Load Estimator gives you a quick, rough estimate of the cooling and heating capacity a room or home needs. Enter your floor area, ceiling height, climate zone, sun exposure, number of occupants, and number of windows, and it returns an estimated cooling load in BTU/hr, a suggested air conditioner size in tons, and a ballpark furnace size.
It is completely free and runs entirely in your browser. Nothing you type is uploaded or stored anywhere, and there are no sign-ups or limits. Use it to sanity-check a quote or plan a project before a professional runs a full Manual J calculation.
Frequently asked questions
- Is the HVAC Load Estimator free to use?
- Yes, it is completely free with no sign-up, no account, and no usage limits. You can run as many estimates as you like.
- Is my data uploaded or stored anywhere?
- No. Every calculation happens locally in your browser. None of the numbers you enter are sent to a server, saved, or shared, so your information stays private.
- How accurate is this HVAC load estimate?
- It is a rough rule-of-thumb estimate meant for quick planning and sanity-checking quotes. It does not account for insulation quality, air sealing, ductwork, humidity, or local design temperatures. For real equipment sizing, have an HVAC professional run a full Manual J load calculation.
- How do you convert BTU to AC tons?
- One ton of air conditioning equals 12,000 BTU per hour, so the tool divides the estimated cooling load in BTU/hr by 12,000. It then rounds up to the nearest half ton, since AC units are sold in standard sizes.
- How many BTU do I need per square foot?
- A common starting point is about 20 to 25 BTU/hr per square foot, which this tool adjusts up or down for climate zone, ceiling height, sun exposure, occupants, and windows. Warmer climates, taller ceilings, and sunnier rooms increase the load.
- Why shouldn't I just buy the biggest system I can?
- An oversized HVAC system short-cycles, turning on and off too quickly. That wastes energy, wears out the equipment, and does a poor job removing humidity. Right-sizing based on an accurate load calculation gives better comfort and efficiency.