20–80 scale
The scouting scale: 50 is major-league average, each 10 points is one standard deviation.
What 20–80 scale means
Every tool grade on the site uses it. 60 is plus, 70 is plus-plus and rare, 80 is the best in baseball. Grades are future projections — what the player should become — not what he is doing today.
What counts as a good 20–80 scale
Higher is better — roughly 40 is poor, 50 average, 60 good, and 70 or better elite.
Also written
scouting_scale · tool_grade · tool_grades · grade · 20_80
Source
FanGraphs