Let me get this straight:
- you want to know how much glycogen we can store.
- you are aware that it depends on the amount of muscle ones carry (which is true)
- you don't know the amount of muscle you have but you want to know ho to find out glycogen storage anyway
It's like asking how many boxes you can fit in a room if you don't know how big the boxes and room are!!!
Liver glycogen is pretty stable with a max of 60-90g of glucose stored
For muscle, it's 14g/kg of muscle mass.
The problem is, as you mention, that it is hard to establish how much muscle you have.
Take someone who is 200lbs with 10% body fat. It would be the normal assumption to say that this individual has 20lbs of body fat and 180lbs of lean body mass and equate this amount of body mass to the amount of muscle we have. This is a mistake. Muscle mass accounts for roughly 40% of our lean mass (the rest being water, bones, skeleton, organs).
In reality this individal would have around 72lbs of muscle mass, or around 33kg.
33kg x 14g/kg = 462g of carbs that can be stored.
In general, the average size male lifter will be able to store anywhere from 350 to 500g of carbs as glycogen.