Free HVAC Calculators

Professional-grade MEP calculators. No login required. Use them as often as you need.

Duct Sizer

Calculate duct size based on CFM, velocity, or friction rate using equal friction or velocity reduction methods.

Recommended Duct Size
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CFM per Diffuser (Balanced)

Distributes total airflow across N diffusers in clean 5-CFM increments so the total stays on target.

Distribution
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Open Advanced Duct Sizer

Pipe Sizer

Size water pipes based on flow rate and velocity limits per ASHRAE guidelines.

Recommended Pipe Size
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CFM / Tonnage Calculator

Convert between CFM, BTU/hr, and tons of cooling. Calculate supply air requirements.

Results
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Psychrometric Calculator

Calculate air properties: humidity ratio, enthalpy, dew point, and wet bulb temperature.

Open Interactive Chart
Air Properties
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Free Desktop Tools

Download standalone desktop versions with additional features. No license required.

PsychChart Pro

ASHRAE-accurate psychrometric calculator with 7 input methods, two-point comparison, air mixing, and chart export.

Download PsychChart Pro

DuctSizer Pro

Round, rectangular, and flat oval duct sizing with CFM per diffuser calculator, round-to-5 balancing, SMACNA table, and constrained sizing.

Download DuctSizer Pro

PlumbingCalc Pro

Plumbing fixture calculator with Hunter's Curve interpolation. IPC 2024, IPC 2021, UPC 2021, and CPC 2022 support. 28 fixture types, 8 building presets, and Revit JSON import.

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Viewer3D Pro BETA

Standalone 3D viewer for BIM models — VTK 9 PBR + HDR image-based lighting + screen-space ambient occlusion. Loads IFC / glb / obj / stl. Section box, WASD navigation, calc-result overlays, camera bookmarks. 4 GB VRAM recommended.

Download Viewer3D Pro

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