Fielding percentage is the most commonly used baseball statistic for fielders at every position.
Add up your putouts and assists. You get an assist when you throw the ball to a teammate who tags or forces the runner out.
Add up your total chances. Total chances are equal to your number of putouts, assists and errors combined. You get an error when you didn't get a putout or assist because you mishandled the ball.
Divide your putouts and assists by your total chances.
Round off to the third decimal place. So, .93051 is .931.