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Advanced HVAC & AC BTU Estimator

Calculate the exact AC BTUs and Tonnage required to cool or heat a room based on square footage, sun exposure, occupancy, and insulation.

Advanced HVAC BTU Estimator

Find the perfect AC size. Don't buy a unit based on square footage alone.

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FAQ

Frequently asked questions

Why isn't square footage enough?
Standard calculators only look at square footage. However, a room facing direct afternoon sun, or a kitchen with an oven, requires significantly more cooling power (BTUs) than a shaded bedroom of the exact same size.
What happens if I buy an AC that is too big?
Bigger isn't always better. An oversized AC unit will cool the room too quickly and shut off before it has a chance to extract humidity from the air, leaving the room feeling cold but 'clammy' or damp.
What is a 'Ton' of AC?
In HVAC terms, 1 Ton of cooling capacity is exactly equal to 12,000 BTUs per hour. This calculator automatically converts your required BTUs into Tonnage for buying central air systems.
How much does a kitchen affect the required BTUs?
According to Energy Star guidelines, you should add a flat 4,000 BTUs to your requirement if the unit is cooling a kitchen, due to the massive heat generated by ovens and refrigerators.
Methodology, assumptions & limitations

How we calculate: This calculator uses standard, peer-reviewed mathematical formulas implemented in TypeScript. All calculations run entirely in your browser — no data is sent to any server.

Assumptions: Unless stated otherwise, calculations assume constant rates over the specified period, no taxes or fees beyond those explicitly input, and standard compounding conventions for the formula type.

Limitations: Results are estimates for planning purposes. Real-world outcomes may differ due to variable rates, regulatory changes, taxes, fees, inflation, or other factors not modeled. This tool does not constitute professional advice.

When NOT to use this: Do not rely solely on this calculator for critical decisions where exact precision is required beyond the decimal places shown.

Feedback: Found an error or have a suggestion? Contact us — we review and correct reported issues within 48 hours.

Deep Dive Guide

Advanced HVAC Sizing: Why Square Footage Fails and How to Calculate True BTUs

Stop buying the wrong size AC unit. Learn the advanced Energy Star calculations that factor in sun exposure, insulation, ceilings, and kitchens to find your exact BTU and Tonnage.

Read Full Guide

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