The best thing to do is find a sanctioned scoring face and shoot a sanctioned round. It is nearly impossible (if not totally impossible) to accurately judge your grouping otherwise. I can't count how many archers think they have 4 inch groups when in reality they are shooting 8-10 inch ones (and get HIGHLY angry that you believe this - well until they shoot an actual round that is absolutely 100% measured).
For instance NFAA has a nice single spot blue face target that is shot at 20 yards. You shoot 60 arrows and score an "x", 5, 4, 3, 2 ,1. it is a 40cm target with each ring adding the same diameter as the others. Therefore each ring (not including the x) is roughly three inches across (x being 1.5 inches across). So, for example, if you shoot 6 inch groups you will be all within the four ring. Not only that but the five is a nice bright white spot in the middle of a dark blue pie plate so it is easy to focus on for us barebow shooters.
You can then compare this to archers around the world as it is a standard round. Anything roughly around a 240 and up (usually all within the three thing - 9 inch group) is quite good. All four ring (six inch and up) will be near world record if not over it. That is, of course, assuming wooden riser/limbs and off the self - Aluminum riser, carbon/foam limbs, and elevated rest can easily add a good 20 points (at least it does for me).
National level scores are in the mid 260's to low 270's. There are only a small handful of people can achieve that with traditional tackle - a larger number can in what the NFAA calls traditional (the afore mentioned aluminum riser setup) but that is till VERY good shooting.
In my experience most shooters will shoot in the 150-180 range. That has some zeroes on the 40cm face but mostly 2's or better. Dedicated shooters will be in the 180-230 range - that ends up being no zeroes and all 2's or better. Those that make a real study of the game and practice well will be 240+ and that will 3's or better. A very very very few world class archers will stay pretty much 4's or better. That leaves a gap of 230-240 - I just do not find that many that average in that range.
Shooting sanctioned targets that you have *no* ability to quibble with on grouping and accuracy is usually a humbling experience - that really tight group you shot at a dandelion usually isn't as tight as you think it is.