HVAC BTU Calculator: Cooling and Heating Size by Square Feet

How to do it

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   Step 1: Open HVAC BTU Calculator: Cooling and Heating Size by Square Feet and add your input

   Type your numbers or text, add your file, or pick the options you need. Nothing is uploaded: everything stays in your browser.

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   Step 2: What HVAC BTU Calculator: Cooling and Heating Size by Square Feet does

   Estimate the BTU and tons of cooling a room or home needs from its area.

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   Step 3: Read the result and compare

   The result appears at once. Change one value to see how the answer moves, then keep the figure that fits your case.

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   Step 4: Copy or save it

   Copy the result or download it. For an important decision, confirm it with the official source or an adviser.

About this tool

Enter the floor area, ceiling height, sun exposure, climate, number of occupants and whether it is a kitchen. The calculator applies the common square-foot rule with adjustments and gives the BTU per hour and the tons of cooling.

The rule of thumb

About 20 BTU per square foot in a mild climate, 25 in a moderate climate and 30 in a hot climate, scaled for ceiling heights above 8 feet. Reduce by 10% for a very shady room, increase by 10% for a very sunny one, add 600 BTU for each person beyond two and 4,000 BTU for a kitchen.

Tons

One ton of cooling is 12,000 BTU per hour. Round to the nearest standard unit size.

Important

This is a quick estimate. A proper Manual J load calculation considers insulation, windows, air leakage and ducts, and is the right method for whole-house systems. An oversized unit cycles too often and handles humidity poorly.

Worked example

A 1,200 ft² home with 8 foot ceilings in a moderate climate, average sun and three occupants needs about 30,600 BTU/h, or 2.55 tons.

Tips for best results

Check every box before you rely on a result, because one wrong digit changes the whole answer. Use the exact figures from your payslip, bill, certificate or contract, and keep a note of the date you calculated. Rates, thresholds and rules change from time to time, so for tax, fees and legal matters treat the output as an estimate and confirm with the official source named on this page. You can run as many scenarios as you like; nothing is saved or sent, and refreshing the page clears the boxes.