What it is

Total Spin is the total revolutions per minute (rpm) on the ball.  This is a combination of Backspin/Topspin, Sidespin and Rifle Spin. Total Spin is not a simple addition of the various types of spin. You can expect the Total Spin on your fastball to increase as your speed increases. You will also notice the type of pitch you throw affects Total Spin. For reference, the average Total Spin rate in an MLB game is 2200+ for a Fastball and 2500+ on a Curveball. 

For the math majors Total Spin = sqrt(Backspin^2 + Sidespin^2 + Rifle Spin^2)

Why it matters

Coaches and scouts are looking for pitchers and pitches that are outside the norm. High spin rate fastballs, typically, tend to ride on a hitter, creating swing and miss, and playing at the top of the strike zone. Low spin rate pitchers are typically creating some sink on their fastball, or the appearance that the fastball is diving.

How it is used

Total Spin can be difficult for an individual pitcher to change although grip adjustments can have some effect.  Understanding if you have a high Total Spin or low Total Spin can help you determine what types of pitches can be most effective for you. For example, a pitcher who tends to have a higher Total Spin may choose to emphasize it by maximizing Vertical Movement, which can be done by focusing on Spin Direction and Spin Efficiency without having to change Total Spin.