Manual J Load Calculator

Calculate the recommended AC system size for your home using a simplified ASHRAE Manual J approach.

Building Information
Standard: 75°F (not adjustable)
Insulation & Construction
Windows & Solar Gain
Air Infiltration & Occupancy
📌 About This Calculator

This is a simplified ASHRAE Manual J approximation (+/- 15-20% accuracy). It provides a ballpark estimate of the cooling load and recommended system size.

When to use:

  • Determining if your system is significantly undersized
  • Rough planning for new construction
  • Identifying problem areas (high solar gain, poor insulation)

When NOT to use: For professional HVAC design, legal disputes, or warranty claims. Always consult a certified HVAC contractor for critical decisions.