You can use a 3D ruler to measure items and distances in the world. To enable/disable this, hit the TAB key, or click the APPS button, and select the command console (the icon that says CMD:\>).
Once in the console, start typing ‘activate’ and select ‘activate 3d ruler’ from the auto-complete menu that appears. Entering this command again when the ruler is active will toggle the ruler off.
Once the ruler is enabled, you can click and drag with your mouse. Coloured axis guides will appear, and a distance counter will become visible on the right of your screen.
