Is the BTU Calculator free?

Yes! The BTU Calculator on CalcSpace is 100 percent free to use: no signup, no ads inside the tool, and no tracking. All math runs locally in your browser.

How do I size an AC with the BTU Calculator?

Enter room size, sun exposure, and occupancy and it estimates the cooling BTUs needed.

Can I use the BTU Calculator on my phone?

Yes. It is fully responsive and runs in any modern browser, on desktop or mobile, with no app to install.

Are my BTU Calculator calculations private?

Completely private. Every calculation runs in your browser with JavaScript; no input or result is ever sent to a server or stored.

BTU Calculator

Calculate the BTU requirements for heating or cooling a room.

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Insulation Quality

Sun Exposure

Number of Occupants

Climate Zone

Cooling BTU Required

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Heating BTU Required

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Recommended AC Tonnage

—

Room Volume

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How It Works

BTU requirements are calculated based on room dimensions, insulation quality, sun exposure, number of occupants, and climate zone. General rule: 20 BTU per sq ft for cooling, 30-40 BTU per sq ft for heating. 1 ton of AC = 12,000 BTU.

About this Calculator

The BTU Calculator is a free, easy-to-use tool for heating, cooling, AC. Simply enter your values and get instant, accurate results — no signup required. All calculations run locally in your browser, so your data stays completely private.

Privacy Note: All calculations are performed locally in your browser. No data is ever sent to a server or third party.

BTU Calculator

How It Works

About this Calculator

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