Calculate residential heating and cooling loads using ACCA Manual J methodology. No signup required.
HVAC Heat Load Calculator
Heating Load— BTU/h
Cooling Load— BTU/h
Recommended System Size— tons
About Manual J: ACCA Manual J is the industry standard for calculating residential heating and cooling loads. This calculator provides estimates for budgeting and preliminary sizing only. Always perform a full Manual J calculation for equipment selection.
What is Manual J?
ACCA Manual J is the standard method for calculating heating and cooling loads in residential buildings. It accounts for heat gain from occupants, appliances, lighting, windows, walls, and infiltration to determine the correct HVAC system size.
✓Heat Gain - Solar radiation through windows, internal heat from people and appliances
✓Heat Loss - Conduction through walls, windows, and infiltration air
✓Latent Load - Moisture removal from humidity
✓Safety Factor - 10-15% oversizing for reliability
Why Use Manual J?
Properly sized HVAC systems save money, improve comfort, and last longer. Undersized systems struggle in extreme weather. Oversized systems short-cycle, wasting energy and wearing out components fast.
Common Sizing Mistakes
✗Oversizing - Using "rules of thumb" like 500 sq ft/ton
✗Ignoring insulation - Not accounting for wall insulation quality
✗Wrong climate zone - Using equipment sized for a different region