<!--
{
  "availability" : [
    "iOS: 13.0.0 -",
    "iPadOS: 13.0.0 -",
    "macCatalyst: 13.0.0 -",
    "macOS: 10.15.0 -",
    "tvOS: 26.0.0 -",
    "visionOS: -"
  ],
  "documentType" : "symbol",
  "framework" : "RealityKit",
  "identifier" : "/documentation/RealityKit/PhysicsMassProperties/mass",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "RealityKit"
    ],
    "preciseIdentifier" : "s:17RealityFoundation21PhysicsMassPropertiesV4massSfvp"
  },
  "title" : "mass"
}
-->

# mass

The mass in kilograms.

```
var mass: Float
```

## Discussion

For a mass of `0` or infinity, the simulation treats the object as
[`PhysicsBodyMode.kinematic`](/documentation/RealityKit/PhysicsBodyMode/kinematic). That is, the object doesn’t respond to
forces.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)