How this calculator works
Estimate the BTU/tonnage needed to heat or cool your space. Values are processed instantly on this device, with checks for missing values and invalid divisions.
Btu: sqft * btu_per_sqft (adjusted for climate, insulation, sun)
Worked example
Enter realistic values in each labeled field, select Calculate, and review both the primary answer and supporting details. Use Reset to clear the form before trying another scenario.
Frequently asked questions
What does the HVAC Sizing Calculator do?
Estimate the BTU/tonnage needed to heat or cool your space.
Are my values stored?
No. The calculation runs locally in your browser and the values are not submitted to us.
Can I rely on this result?
Use this as an informational estimate. Check measurements and source values before acting on the result.