HVAC Load Calculator Manual J

BTU Sizing for Contractors

Free · In‑App Purchases · Designed for iPad

The Manual J load calculator HVAC contractors actually want to use. Stop paying $40 for clunky, over-engineered calculators designed for engineers. HVAC Load Calculator brings professional Manual J calculations to your iPhone or iPad — clean, modern, offline-ready, and built for the field. BUILT FOR HVAC PROFESSIONALS Unlike expensive desktop software shoehorned onto mobile, we designed this from scratch for techs working in the field. Large buttons you can tap with gloves on. Fast calculations while standing in a basement. Professional reports that win homeowner trust. THREE LEVELS OF ACCURACY Simple Mode – 8 inputs Regional ZIP-code benchmarks and square-footage multipliers. Get an estimate in under 60 seconds with zero measurements. Perfect for quick quotes and initial sales conversations. Moderate Mode – 15 inputs Component-level factors: insulation quality, window types, foundation — with a conservative safety buffer. Prevents undersizing while staying accessible for non-engineers. The sweet spot for standard replacement jobs. Pro Mode (Manual J) – 16 inputs + pro overrides Full MJ8 physics: altitude-adjusted density, solar load factors, CLTD daily-range lag, and separated duct analysis. Maximizes equipment life and comfort — often right-sizing by 1+ ton. Best for new construction, high-performance builds, and detailed equipment sizing. NOW AVAILABLE WORLDWIDE International mode lets you enter your city, country, and local design temperatures directly — no ZIP code required. Choose your climate zone and moisture regime, and the calculator handles the rest. US Mode: ZIP code lookup with 80+ city climate database International Mode: Manual location and design temperature entry Metric Units: Toggle between Imperial and SI (kW, m², m³/h) throughout the app and PDF reports WORKS IN THE FIELD Offline-First – No signal in the basement? No problem. Everything runs locally on your device. Auto-Save Projects – Every calculation saves automatically. Never lose your work. Professional PDF Reports – Generate and share detailed load reports from your iPhone or iPad. Site Photo Documentation – Capture tagged photos, label by location and component, add notes, and include a professional photo appendix in your reports. iPad Support – Optimized layouts give you more room to work on-site or back at the office. THE MATH YOU TRUST Calculations follow ACCA Manual J 8th Edition methodology: – Cooling BTU/hr (sensible and latent loads) – Heating BTU/hr – Recommended tonnage (rounded to 0.5 tons) – Recommended furnace size (rounded to 5,000 BTU) – Manual S equipment sizing guidance – Kitchen/appliance heat gain per MJ8 Table 4 Tap “How Our Calculator Works” for a plain-English guide to every input and how it shapes your results. WHY CONTRACTORS CHOOSE US – Modern, intuitive interface that makes sense the first time you use it – Dark mode and system theme support – Fast performance, even on older iPhones – Privacy-first: your data stays on your device – Free to try — 7 days free, then $4.99/year PERFECT FOR HVAC contractors, installers, and service techs Sales teams quoting new systems Independent contractors building their business International professionals working in metric Home inspectors documenting HVAC systems No account. No setup. Just open the app and get to work. Terms of Use (EULA): https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

Ratings & Reviews

  • 5.0
    out of 5
    8 Ratings

-Updated language

Version 1.9.5 (54)

The developer, Mike Watson, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .

  • Data Not Collected

    The developer does not collect any data from this app.

    Privacy practices may vary, for example, based on the features you use or your age. Learn More

    Accessibility

    The developer has not yet indicated which accessibility features this app supports. Learn More

    Information

    • Seller
      • Mike Watson
    • Size
      • 59.7 MB
    • Category
      • Utilities
    • Compatibility
      Requires iOS 15.1 or later.
      • iPhone
        Requires iOS 15.1 or later.
      • iPad
        Requires iPadOS 15.1 or later.
      • iPod touch
        Requires iOS 15.1 or later.
      • Mac
        Requires macOS 12.0 or later and a Mac with Apple M1 chip or later.
      • Apple Vision
        Requires visionOS 1.0 or later.
    • Languages
      • English
    • Age Rating
      4+
    • In-App Purchases
      Yes
    • Copyright
      • © 2026 Mike Watson
  • Developer Website
  • Privacy Policy

    • More by Mike Watson