Heat Load Calc HVAC

HVAC Heat Load BTU Calculator helps HVAC technicians, engineers, and contractors calculate accurate cooling and heating loads. Calculate accurate cooling and heating loads using a simplified ACCA Manual J methodology based on room dimensions, insulation levels, window types, and ASHRAE climate zones - the industry standard for professional air conditioning system sizing. LOAD CALCULATION MODES: Cooling Mode - Calculate BTU/h cooling requirement for air conditioning Heating Mode - Calculate BTU/h heating requirement for furnace and heat pump sizing Automatic Tonnage Conversion - Get AC tonnage (0.5 to 5+ tons) from load results CFM Requirement - Airflow from the supply-air temperature difference, around 400 CFM per ton ROOM PARAMETERS: Room Dimensions - Enter length, width, and ceiling height Exterior Walls - Count how many of the room's walls face outdoors Insulation Levels - Poor, Average, Good, or Excellent, mapped to assembly U-factors Window Types - Single Pane, Double Pane, Triple Pane, Low-E, with U-factor and SHGC Window Orientation - North, East, South, West or mixed exposure for solar gain Floor Type - Over conditioned space, over crawlspace/garage, or slab on grade Climate Zones - 5 zones with ASHRAE design temperatures, overridable by hand Duct Location - Add duct gain/loss when the ducts run through unconditioned space Occupant Load - Sensible and latent heat from building occupants COMPONENT BREAKDOWN: Wall conduction load Window conduction and SHGC-based solar gain, shown separately Ceiling and roof heat gain Floor and slab-perimeter load Infiltration load from envelope tightness Occupant sensible and latent heat Duct gain/loss in unconditioned space Sensible and latent totals, tonnage, airflow and BTU/h per sq ft OPTIONAL PRO UPGRADE — $2.99 ONE-TIME IN-APP PURCHASE The following features require a separate one-time in-app purchase. They are not required to use the calculator: • Unlimited saved calculation history • PDF export of results • Dark theme • Ad-free experience WHY HVAC PROS USE THIS CALCULATOR: Faster Manual J estimates than spreadsheets or online calculators Accurate BTU sizing prevents oversized/undersized systems Reduces callbacks from incorrect system selection Quick cooling load checks on service calls ASHRAE-compliant Manual J methodology for commercial work Improves customer confidence with detailed technical reports PERFECT FOR: HVAC design engineers sizing air conditioning systems HVAC field technicians quick-checking load requirements AC contractors preparing accurate equipment bids HVAC apprentices learning Manual J methodology Building maintenance engineers planning replacements Residential and commercial HVAC system sizing Energy auditors estimating cooling needs Based on ACCA Manual J design methodology: assembly U-factors, SHGC-based solar gain, ASHRAE design conditions, and no arbitrary safety padding. Part of HVACTools Suite - the professional HVAC technician app for field calculations, refrigeration diagnostics, and air conditioning system design.