Calculate percentage of used memory

I have create a graph for my lxc containers. Now I use “maxmem” and “mem”. But the graph is getting a little big. Is het possible to calculate a percentage with is data. So I can get a graph with only percentage of used memory.

InfluxDB does not support this use case very well. Maybe if you switched query editor mode to text editor, then you can write sub queries. But not sure exactly what that would look like.