Stelid
Free tool · HVAC

HVAC heat-load sizing calculator

Estimate BTU/hr requirements from square footage, climate zone, ceiling height, insulation, and window area.

A quick Manual J-style estimate. Not a substitute for a full Manual J, but accurate enough to ballpark a tonnage on-site before you commit.

Cooling load
77,920 BTU/hr
Recommended unit
6.5 tons
Heating load (rough)77,920 BTU/hr
BTU/sqft43.3
  • · Approximation only — not a substitute for a full Manual J calculation.
  • · Doesn't account for window orientation, occupant load, or duct losses.
  • · At 5 tons or above, consider zoning or a dual-system design.
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The same calculator runs inside Stelid — pre-filled with your job, customer, and pricebook data. No copy-paste.

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