# Sandbox.PhysicsBody.RebuildMass

```csharp
void RebuildMass()
```

Meant to be only used on dynamic bodies, rebuilds mass from all shapes of this body based on their volume and [physics properties](/api/Sandbox.PhysicsBody/Surface), for cases where they may have changed.

Declared in [Sandbox.PhysicsBody](/api/Sandbox.PhysicsBody).
Assembly: `Sandbox.Engine`.