Mini Split Sizing Calculator: HVAC BTU Load Calculator

Overview

A Manual J-Style Load Estimate, Made Simple

The calculator above starts from your room's square footage, then adjusts that baseline with the kinds of factors a Manual J load calculation looks at — outdoor design temperature for your ZIP code, ceiling height and volume, glass and doors, air leakage, ventilation, and internal gains. It returns a BTU/h load per room and the DIY mini split systems that match, and the optional emailed report spells out the breakdown behind the number. The math runs in your browser: no account, nothing to download, and the email step is optional (just hit Skip).

Want the detail? How it works walks through the method step by step, the sizing FAQ covers oversizing, rounding between sizes, and room-by-room vs whole-home, and about explains where the math comes from and what this tool is (and isn't) good for.

Reference Index

Sizing Guides & Resources