HVAC Load Calculator

Professional Manual J calculations designed for HVAC contractors.

Stop paying $40 for clunky engineering software. Get accurate load calculations on your iPhone, completely free.

Three Calculation Modes

Simple - 8 inputs, ±15-20% accuracy
Quick quotes when you’re standing in someone’s basement.

Moderate - 15 inputs, ±10-15% accuracy
The sweet spot for most residential jobs.

Comprehensive - 25+ inputs, ±5-10% accuracy
Full precision for complex projects.

Built for Field Work

✓ Works offline - No cell service required
✓ Auto-saves - Never lose your calculations
✓ ZIP code lookup - Instant climate data for 80+ cities
✓ PDF reports - Professional exports for customers
✓ Fast & modern - Built from scratch for iPhone

Common Questions

How do I choose which calculation mode?
Start with Moderate for most jobs. Use Simple when speed matters more than precision. Use Comprehensive when you need maximum accuracy.

Where is my project data stored?
All projects save automatically to your iPhone. Your data stays on your device - no cloud uploads.

Can I use this offline?
Yes! The app works completely offline. All calculations and climate data are built in.

What if my ZIP code isn’t in the database?
The app uses smart fallback logic (same area → same region → US averages). You can also manually enter custom degree day values.

Is there a limit on projects?
No limits. Create as many projects as you want.

What iOS version do I need?
iOS 15 or later. Works on iPhone and iPad.

Get Help

Email: mike@productparty.us

We typically respond within 24-48 hours on weekdays.

Found a bug? Email us with what you were trying to do, what happened instead, and your device/iOS version.

Feature request? We’re actively developing based on contractor feedback. Send your ideas.