Size Every Job Right. Stop Leaving BTUs on the Table.
Accurate Manual J sizing means fewer callbacks, lower warranty claims, and customers who refer you instead of replacing you.
Instant download · Works in any field condition · Based on Manual J & Manual S
Oversized equipment short-cycles. Undersized equipment runs 24/7 and kills compressors. One wrong calc costs more than this guide.
Manual J, Manual S, and the AI Prompts to Back Them Up
Complete Manual J Quick-Reference Cheat Sheet
The residential load calculation formulas you need on every install — organized for field use, not textbook reading.
- Residential heat gain/loss formulas
- Room-by-room BTU breakdown template
- Equipment sizing selection guide (Manual S)
- Ductwork airflow cross-reference
ChatGPT Prompt Templates for Load Calcs
Paste in room data and get structured output — manual J calculations with flagged sizing errors, no software required.
Climate Zone Reference Table
Design temperatures and climate zone data for every region — look up the correct values before you run the numbers.
Common Sizing Mistakes (Checklist)
The calculation errors that generate the most callbacks — with a checklist to catch them before you spec the equipment.
Instant Download
PDF plus accessible formats — works on your phone, tablet, or printed and laminated for the truck.
Built for the Tech Who Sizes the Job Before Touching a Unit
The Estimating Tech
You're quoting a new install and don't want to eyeball it. Do it right the first time.
The Service Manager
Your team keeps calling back on oversized units. You need a consistent sizing process.
The HVAC Student
Manual J is on every licensing exam. Get a field-ready reference that actually makes sense.
From Techs Who Got the Sizing Right
“Caught a 2-ton overage on a new construction job that would've short-cycled all summer. The Manual S selection guide showed me exactly where the original spec went wrong. Worth every penny.”
Marcus T.
Install Tech, Phoenix AZ
“Manual S selection was always the piece my techs skipped. They were sizing by gut feel on the equipment side. Now they have a reference they actually use in the field.”
Ray D.
Service Manager, Tampa FL
“I use the ChatGPT prompts to double-check my estimates on the job site before I commit to a unit. Takes two minutes and has saved me from a bad call twice already.”
Chris V.
Lead Tech, Denver CO
Accurate Sizing Is the Difference Between a Callback and a Referral.
One guide. One download. No more eyeballing tonnage.