HVAC Load Calculator Manual J

The Manual J HVAC Load Calculator built for professionals who work in the field, not in a conference room.

Stop overpaying for clunky, over-engineered calculators designed for engineers. HVAC Load Calculator brings professional Manual J calculations to your phone or tablet: clean, modern, offline-ready, and built for the field.

BUILT FOR HVAC PROFESSIONALS
Designed from scratch for techs in the field: large buttons you can tap with gloves on, fast calculations in the basement, and professional reports that win homeowner trust.

THREE LEVELS OF ACCURACY

Simple Mode
Sized from your ZIP code's design conditions and the home's floor area. Get an estimate in under 60 seconds with zero measurements. Perfect for quick quotes and initial sales conversations.

Moderate Mode – Standard Accuracy (Whole-House Block Load)
Component-level factors: insulation quality, window types, foundation. The sweet spot for standard replacement jobs.

Pro Mode – Professional Grade (Detailed Whole-House Block Load)
Full MJ8 detail: per-direction window solar, measured airtightness, window ratings, overhang shading, and duct analysis. Maximizes equipment life and comfort, often right-sizing by 1+ ton. Best for new construction, high-performance builds, and detailed equipment sizing.

SHOW THE HOMEOWNER THE NUMBERS
Operating Cost Estimates – See the estimated annual heating and cooling cost of the recommended system, built from your local climate data and energy prices, right on the results screen and in the report.
Proposal PDF – Turn a load calculation into a clean Good/Better/Best system options proposal, with the full load calculation attached behind it.

WORKS IN THE FIELD
Offline-First – No signal in the basement? No problem. Everything runs locally on your device.
Add Rooms – Build the load room by room with a tape measure. Enter each room's size and windows, and the floor area, ceiling height, glass and exterior wall area total up for you. The room list goes on your PDF report.
Auto-Save Projects – Every calculation saves automatically. Never lose your work.
Professional PDF Reports – Generate and share detailed load reports from your phone or tablet. Add client name, site address, and job number; every report is stamped with a revision number and date, so everyone knows it's the latest version.
Site Photo Documentation – Capture tagged photos, label by location and component, add notes, and include a professional photo appendix in your reports.
Tablet 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
– Recommended furnace size
– Manual S-based equipment sizing guidance
– Kitchen and appliance heat gain

If a result looks unusual for the home's size, the app flags it before the report goes out.

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 devices
– Privacy-first: your projects stay on your device, never on our servers
– Free to download: try it on your first calculations before subscribing

PERFECT FOR
– HVAC contractors, installers, and service techs
– Sales teams quoting new systems
– Independent contractors building their business
– Home inspectors documenting HVAC systems

Available in the United States and Canada. No account. No setup. Just open the app and get to work.

Try it free, then keep going with a subscription. Cancel anytime.

Recent changes:
Team access: if your company provides the app for its crew, your company's access code or device management now unlocks it. Settings > Subscription > Team Access Code.

The ZIP code now comes first on a project, and if it's missing, Calculate takes you straight to it. Each calculation mode now says what it gets you.