HVAC Load Calculator
US · Manual J 8th EditionRun a real Manual J at the kitchen table. Equipment sizing, climate data by ZIP, and a homeowner-ready PDF with your logo on it.
Four apps · One toolbag
Field math for HVAC pros. Done on the phone, defended at the door.
An HVAC load calculator for the US and Canada, duct sizing with static pressure checks, and A2L refrigerant charging. Start with the free online Manual J load calculator in your browser, or take the full apps offline. Every one of them works without a signal, states its assumptions, and gives you a number you can put in front of a homeowner or an inspector.
- Offline first
- Real standards, named sources
- Built by one shop, used in the field
Heat Pump Sizing Canada
Canada · CSA F280-12F280-based loads with NRCan design temperatures by postal code. Metric first, English and French, built for Canadian winters.
Static Pressure & Duct Check
US · Manual D methodsThe ductulator in your pocket — forward and reverse — plus static pressure checks and a full Manual D system designer with PDF export. Free, fully offline.
A2L Certification Test Prep
R-454B · R-32 · R-410A300+ practice questions for the A2L / Low GWP safety exam, plus superheat, subcooling, and max allowable charge for A2L refrigerants with glide handled right. Free, no account.
Why these apps
Built like you'd want them built.
- Offline first. Crawlspaces, mechanical rooms, and new builds with no service. Every calculation runs on the phone. Nothing waits on a signal.
- Honest math. Results show what they assumed. A defaulted friction rate or an assumed equipment rating never hides in the fine print.
- Named sources. ASHRAE design temperatures, NRCan HOT2000 weather stations, ACCA Manual J and Manual D methods, UL and ASHRAE charge limits. Methodology language only — never “approved” or “certified.” The data behind every number is cited in the app.
- Made for the truck. Big targets, few inputs, results you can screenshot and text to the office. Skimmable one-handed between calls.
Free in your browser
Free HVAC load calculator and field guides — no download, no account.
Run a free online Manual J load calculation right here, size a duct run, or check superheat on an A2L system. Every tool is free, works in the browser, and states its assumptions. When the signal dies in a crawlspace, the full apps do the same math offline.