The NRA established two 100yd smallbore targets that have the 10-ring or X-ring @ 1moa or 1"...depending on the specific target being shot.
Essentially, that set the bar for competition shooting...many yrs ago. Now, groups are typically judged by MOA (measured center to center from the two furthest shots).
Pellets, being slow and draggy, tend to be very difficult to shoot into 1moa @100yds, esp with higher shot counts (3 vs 5 vs 10 shots, etc.).
It is also difficult to measure "one hole" groups (multiple shots), which is why many 100yd smallbore competitions feature 1-shot-per-target for score (this also helps with cheating, eliminating the need for moving backers).
If you want to compare with others, use MOA (or MILs, if you're metric). I usually just write mine down in my log (in inches v yardage, which is an easy conversion to MOA if I want) and just try to get better.