Is there a way to figure out how much weight resistance bands offer?

I been doing an exercise routine that requires using bands at a gym with weights attached. Currently I don’t have a gym membership and so I have been trying to keep up my workouts at home.
I’ve been doing side leg lifts with resistance bands and by extending the band I can make the resistance less or more by shortening it.
So I was wondering if there is a way to calculate exactly how much weight I am using?