i have tried to wiegh out a gram before vaping, and then wieghed it again afterwards. the avb wieghed about 0.6g. there is a thread about this somewhere... although i don't know if anyone was able to report back with any reliable results.
i think there would be a lot of variables to account for, i.e. you would probably get different results each time you measured a gram before/after vaping.
if you want to have anything close to an accurate idea of what you got, you need a scale. i think there is a thread about scales around here too.
or find a friend who has a scale, then measure what you currently have in the jar. so next time you 'fill' it you will be able to assume you have X amount of grams in the jar.
or maybe someone will post a pic like you asked...