Professional HVAC Calculators
Free tools for load calculations, duct sizing, refrigerant charge, psychrometrics, and system design. Built for HVAC technicians and contractors.
Load Calculations
Calculate heating and cooling loads for residential and commercial buildings
Ductwork & Airflow
Size ducts and calculate airflow requirements
Duct Sizing Calculator
Size rectangular and round ducts based on CFM and friction rate.
CFM Calculator
Calculate airflow requirements based on room size and air changes.
Air Velocity Calculator
Calculate velocity and pressure relationships in ductwork.
Ventilation Rate Calculator
Calculate outdoor air requirements per ASHRAE 62.1.
Refrigeration & Charging
Refrigerant calculations and system diagnostics
Refrigerant Charge Calculator
Calculate refrigerant charge for system commissioning.
Superheat Calculator
Calculate target superheat for TXV and fixed orifice systems.
Subcooling Calculator
Calculate subcooling for proper refrigerant charge verification.
P-T Chart Calculator
Pressure-temperature lookup for common refrigerants.
Psychrometrics & Comfort
Air property calculations and comfort analysis
Equipment & Utilities
Equipment sizing and utility calculations
Tonnage Calculator
Convert between BTU/h and tons of refrigeration.
Gas Pipe Sizing
Size natural gas and propane piping per fuel gas code.
Fan Laws Calculator
Calculate fan performance at different speeds and conditions.
Blower Door Analysis
Analyze building envelope leakage from blower door tests.
Room Pressurization
Calculate airflow for positive/negative pressure rooms.
HVAC Unit Converter
Convert between HVAC units: BTU, tons, CFM, and more.
Reference Tables
Quick reference guides and data tables
Why Use Our Calculators?
Works Offline
Install as PWA. All calculations run locally in your browser.
ASHRAE Based
Based on ASHRAE standards and industry best practices.
No Login Required
Start calculating immediately. No account needed.
Mobile Friendly
Use on phone, tablet, or desktop on the job site.