HCLHVAC Cost Lab

Calculators / System sizing

System sizing

Air Conditioner BTU Calculator

Get a first-pass cooling capacity for planning. The tool adjusts a square-foot baseline for room volume, climate, insulation, and solar exposure.

Your planning inputsUpdates automatically
sq ft
Include only the area served by this system.
ft
Vaulted ceilings increase the air volume.
Choose the closest design condition.
Windows, air leakage, attic insulation, and wall insulation.
Large west-facing windows can raise peak load.

Estimated result

44.4k BTU/h

First-pass nominal size: about 3.5 tons. A professional load calculation may select a different sensible/latent capacity.

How to use this estimate

  • The result is a preliminary capacity target, rounded to common nominal sizes.
  • If the proposed system is substantially larger, ask for the room-by-room load calculation.
  • Smaller properly sized systems usually control humidity and cycle more consistently than oversized systems.

Transparent method

We expose the planning formula so you can challenge it and replace assumptions with local evidence.

floor area × 22 BTU/h × ceiling factor × climate factor × insulation factor × exposure factor

What this calculator cannot see

  • Occupants, ventilation, glazing area, orientation, infiltration, ducts, and local design temperatures require a professional load calculation.
  • Do not purchase equipment from this estimate alone.

Professional verification

Use this result to prepare questions and compare scenarios. Final equipment selection, electrical work, refrigerant work, combustion, duct design, and permitting should be handled by qualified professionals following local codes and manufacturer instructions.