HVAC Heat Load BTU Calculator

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 — See required airflow for proper system balance

ROOM PARAMETERS:
Room Dimensions — Enter length, width, and ceiling height
Insulation Levels — Poor, Average, Good, or Excellent with correction factors
Window Types — Single Pane, Double Pane, Triple Pane, Low-E glass options
Climate Zones — 5 zones from Hot to Cold with design temperatures
Occupant Load — Account for sensible heat from building occupants

COMPONENT BREAKDOWN:
See loads from walls (exterior and interior)
Window gain/loss calculations
Ceiling and roof heat gain
Floor infiltration and air leakage
Occupant sensible heat contribution
Component-by-component analysis for system design

PROFESSIONAL TOOLS:
Save calculation history for project reference
Export results to PDF for professional job estimates
Works 100% offline — no internet for job sites
English & Spanish support for crews
Dark theme for outdoor fieldwork

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 simplified ACCA Manual J design methodology.

Part of HVACTools Suite — the professional HVAC technician app for field calculations, refrigeration diagnostics, and air conditioning system design.