ダクト計算 Pro

Whether on-site or in design, this single tool handles all your duct calculations. Duct Calculation Pro brings the calculations you use daily in HVAC and ventilation design to your smartphone, completely offline.

■ Free and ready to use
- Duct size selection (equal friction method, circular) — Calculates the required diameter from airflow and unit friction loss, and displays recommended sizes for spiral ducts.
- Unit conversion — Converts between airflow, wind speed, and cross-sectional area. One-tap switching between m³/min, m³/h, and L/s

■ More features in Pro
- Rectangular duct conversion — Calculates long side × short side (rounded to 50mm) from equivalent diameter, with aspect ratio warning
- Airflow calculation — Calculates airflow from duct diameter + wind speed, or duct diameter + friction loss
- Air outlet selection — Calculates approximate neck size, effective area, and reach distance from airflow and neck wind speed
- Static pressure calculation — Sum of straight pipe losses + local losses of fittings (elbows, branches, expansion/contraction)

■ Design tailored to practical use
- Airflow units are m³/min, m³/h, and L/s; dimensions are mm — aligns with Japanese design practices
- Calculation basis displayed on each screen — Understand what was calculated and how
- Results can be copied and pasted into notes or drawings

■ For both on-site and design work
- Fully offline — Operates even in machine rooms and new construction sites where radio waves cannot reach.
* Larger control panel, screen never turns off (wakelock), no account required.
* Input values ​​do not leave the terminal.

■ One-time purchase
The free version includes full functionality for duct size selection and unit conversion (no feature limitations). Duct Calculation Pro is a one-time purchase and removes features such as rectangular duct conversion, airflow inverse calculation, air outlet selection, and static pressure calculation.

No subscriptions. No ads. No feature removals after the fact.

This is a reference calculation. For detailed design, please be sure to verify with relevant standards (Handbook of Air Conditioning and Sanitary Engineering, ASHRAE Fundamentals, etc.) and each product catalog.