Air Velocity Calculator

Calculate air velocity from airflow and duct size, or estimate airflow from measured velocity for MIWIND fan, fresh air and exhaust fan projects.

Open calculator View fan products

v = Q / A Q(m³/s) = Q(m³/h) / 3600 Fan airflow, duct area and site velocity in one practical check.

Air volume and velocity reference

Use this calculator as an engineering reference when comparing MIWIND duct fans, fresh air units and exhaust fans. Enter airflow and duct area to estimate velocity, or enter measured velocity and section size to estimate airflow. Final product selection should be confirmed against product specifications and project conditions.

Air volume Q m³/h Section shape Diameter D mm

Measured velocity points comma, space or line separated m/s values

Result Enter positive values to calculate.

Section area -- m²

Average velocity -- m/s

Engineering reference only. Confirm final selection with MIWIND.

Recommended products for this result

Calculate airflow to see the closest MIWIND product paths.

Complete calculation formulas

Air velocity from air volume

v = Q / A

Use Q in m³/s. When air volume is given in m³/h, first use Q(m³/s) = Q(m³/h) / 3600.

Air volume from velocity

Q = v × A × 3600

Use velocity in m/s and area in m² to estimate air volume in m³/h.

Circular duct area

A = π × (D/1000)² / 4

D is duct diameter in millimeters. Dividing by 1000 converts millimeters to meters.

Rectangular duct or outlet area

A = (W/1000) × (H/1000)

W and H are width and height in millimeters.

Average measured velocity

v_avg = (v1 + v2 + ... + vn) / n

Take several anemometer readings across the opening and use the average for field checks.

How to measure air velocity on site

Confirm section shape

Measure the circular duct diameter or the rectangular outlet width and height in millimeters.

Check multiple points

Use an anemometer at several points across the duct or grille instead of relying on one center reading.

Calculate reference value

Average measured velocity, calculate air volume, then compare the result with MIWIND product specifications.

Confirm before selection

Send air volume, duct size, noise target and installation condition so MIWIND can confirm the model.

Use the value with product specifications

For duct fan and fresh air systems

Velocity helps compare airflow target, duct section and comfort/noise requirements before checking product curves.

For exhaust fan projects

Measured velocity at the outlet can be converted into approximate air volume for site verification.

Engineering reference only

The calculator does not replace fan curve checks, pressure loss calculation, installation review or MIWIND model confirmation.

Related MIWIND Products

Fan, fresh air and exhaust products commonly checked with airflow and air-velocity calculations.

Need model confirmation?

Share airflow target, duct size, installation condition and measured velocity. MIWIND can confirm the suitable product range and specification match.