HVAC Tools Library
Browser-based calculators and reference tools for air balancing and HVAC work. All calculations happen in your browser — no data is sent anywhere, no account required.
📝 Educational use
Available Calculators
Air Changes per Hour (ACH) Calculator
Enter supply airflow (CFM) and room dimensions to calculate ACH. Compare results against ASHRAE reference values for common space types.
Open calculator →CFM Variance Calculator
Enter design and measured CFM to calculate the difference and variance percentage. Commonly referenced tolerance is ±10%, but requirements vary by project specifications and TAB standard.
Open calculator →Fan Law Calculator
Enter original fan speed (RPM), CFM, static pressure, and horsepower alongside a new RPM to see how airflow, pressure, and power change using the fan affinity laws.
Open calculator →Air Density Correction Calculator
Enter altitude and air temperature to estimate how air density differs from standard conditions and convert actual CFM (ACFM) to standard CFM (SCFM).
Open calculator →Ak Factor Register Airflow Estimator
Estimate airflow (CFM) at a supply register, return grille, or diffuser from face velocity and manufacturer Ak factor. Includes explanation of what Ak factor means and why manufacturer data is required.
Open calculator →Planned Tools
These tools are in development. Cards are listed here for reference — no separate pages yet.
Duct Traverse Point Planner
Enter duct shape and dimensions to see the number and position of traverse measurement points using the Equal Area Method.
Static Pressure Drop Estimator
Estimate friction loss from duct length, size, and airflow. Helps explain why system resistance affects air balance.
Supply / Return CFM Balance Checker
Enter total supply and total return CFM to calculate imbalance percentage and understand pressurization effects.
Outdoor Air Fraction Calculator
Estimate the percentage of outside air vs. recirculated air in a mixed-air system.
Ventilation Rate Estimator
Estimate minimum outside air requirements from occupancy and floor area using the ASHRAE 62.1 Ventilation Rate Procedure.
About these tools
ABS calculators are provided for educational purposes and general estimation. Results should be verified against project specifications, applicable mechanical codes, and the judgment of qualified engineers and TAB professionals. Tolerance requirements and acceptance criteria vary by project, contract, and applicable standard.