ManualJ Lite

ManualJ Lite is a fast, offline HVAC load calculator based on the Manual J simplified method. Enter your building details and instantly get cooling and heating load estimates for proper equipment sizing. WHAT IT CALCULATES: Cooling Load: - Sensible and latent cooling loads (BTU/h) - Total cooling capacity required - AC tonnage recommendation - Load breakdown by component Heating Load: - Total heating BTU/h - Heat loss through walls, windows, roof - Infiltration losses - Recommended furnace capacity BUILDING INPUTS: - 7 IECC climate zones (Zone 1 through Zone 7) - Floor area in square feet - Insulation quality (Poor, Average, Good, Excellent) - Window type (Single, Double, Low-E Double, Triple) - Number of stories and orientation KEY FEATURES: - Simplified Manual J calculation method - Cooling and heating mode toggle - Component-level load breakdown percentages - Instant results as you adjust inputs - Clean, easy-to-read results layout - Works completely offline - No account or login required BUILT FOR HVAC TECHS: Whether you are an HVAC technician, contractor, or homeowner planning a system upgrade, ManualJ Lite gives you quick load estimates for equipment sizing. Select your climate zone, enter building specs, and get BTU and tonnage results in seconds. Covers all 7 IECC climate zones with appropriate design temperatures for accurate residential load calculations.