HVAC Load Calculator
Get a rough whole-house heating and cooling load in BTU and tons from the floor area, climate-based factors, window count, and occupants. Calculates in your browser.
Cooling load
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Show the math
Each load scales the floor area by a climate-based factor:
heating = area × heating factor
cooling = area × cooling factor + windows × 1,000 + occupants × 600
Factors depend on climate and insulation, mild, well-sealed homes use lower numbers than cold or leaky ones. This is a simplified estimate, not a certified Manual J. All math runs locally in your browser.
What this does
An HVAC load calculator gives a rough whole-house heating and cooling load in BTU and tons from the floor area, climate factors, window count, and occupants.
How to use it
- Enter the floor area.
- Set the climate factors.
- Add windows and occupants.
- Read the heating and cooling load.
How it works
Climate-based BTU-per-square-foot factors scale with insulation and weather. It is a ballpark, not a substitute for Manual J.
load = area × factor + windows + occupants
Understanding your result
Treat this as a ballpark for whole-house sizing, not a substitute for a Manual J calculation. The common and costly mistake is oversizing, which causes short-cycling, uneven temperatures, poor humidity control, and higher bills, so before buying equipment have a proper load calculation done rather than matching or exceeding whatever unit you currently have.
Example
A 2,000 sq ft home often lands near 3 tons of cooling.
Sources & methodology
Last updated .
Frequently asked questions
How do I size a furnace or AC?
Estimate the heating and cooling load in BTU, then choose equipment that meets it without large oversizing. This tool gives a ballpark figure.
What are the heating and cooling factors?
They are BTU per square foot for your climate and insulation, milder, well-insulated homes use lower factors than cold or leaky ones.
Is this a substitute for Manual J?
No. It is a simplified estimate; a certified Manual J calculation is the standard for equipment sizing.
Is my data saved?
No. Everything is calculated locally in your browser.
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