SOLIDWORKS 2016 has made enhancements to the intersect feature. This makes it much easier to create the fluid volume inside a tank or other fluid vessel.

Use Design Studies to iterate the different volumes and output the gauge chart. This also helps find the fluid height in a tank for a predetermined outage (common in the oil industry).

Watch this video to learn more.

https://youtu.be/bURiSJr1wNw

What other methods do you use?