# Aerodynamic and Aeroacoustic Measurements

Change the default unit system, create custom units, and measure geometry features.

## Unit System of Imported File

It is assumed that the imported surface mesh of the object, for example, vehicle, is in meters (m).

Use the Unit System Selector to change the current unit system.

## Recognized Units

Types of units recognized by HyperMesh CFD.

**Unit Type****Recognized Units**- Length
- mm, cm, m, in, ft, dm
- Mass
- mg, g, kg, ounces, lb, slug, mkg, gkg
- Weight
- N, lbf, kN, MN, GN, kgf, dyn, gf
- Force
- N, lbf, kN, MN, GN, kgf, dyn, gf
- Torque
- N*mm, N*cm, N*m, in*lbf, ft*lbf, kGf*m, dyn*cm
- Pressure
- Pa, kPa, MPa, GPa, N/mm2, N/m2, bar, psi, TPa, kbar, Mbar, lbf/in2, lbf/ft2
- Time
- s, ms, us
- Angle
- deg, rad

## Change the Unit System

Use the Unit System Selector to set the current unit system.

Most numbers in a model have units associated with them, such as centimeters or inches for length, and kilograms or slugs for mass. Units are always displayed to the right of numbers wherever they appear.

When you enter a number in a field, the appropriate unit is automatically appended.
If you type a unit after a number, the number is converted to the current units. For
example, entering `10 in`. inside a field where millimeters are
the current units results in `254 mm`. being displayed.

Units are displayed with mixed capitalization for readability, but you can use any combination of upper and lower case letters when you type them.

## Measure Features

Use the Measure tool to measure geometry features including lengths, angles, and the dimensions of a bounding box.

Click the satellite icon that appears when you hover over the Measure tool to view a list of all measures in your model.

- Measurements persist after you exit the tool, are listed in the Model Browser, and dynamically update when you make changes to the geometry.
- When you double-click a length measure in the modeling window, it gives you the x, y, z components of the distance vector in the global system.

### Measure Bounding Box Dimensions

Use the Measure Box tool to measure the dimensions of the bounding box for a selected part or generated shape.

### Measure Angles

Use the Measure Angle tool to measure an angle defined by three points.

### Measure Distance

Use the Measure Length tool to measure the distance between two points.

### Measure Length

Use the Measure Length tool to measure not only the length of an edge, but also the radius of a circle or an arc, and the diameter or length of a cylinder.