The image above represents the mill speed.

To compute for mill speed, two essential parameters are needed and these parameters are **Speed Percentage (N%)** and **Critical Speed (N _{c}).**

The formula for calculating mill speed:

MS = N% x N_{c}

Where:

MS = Mill Speed

N% = Speed Percentage

N_{c} = Critical Speed

Let’s solve an example;

Find the mill speed when the speed percentage is 12 and the critical speed is 10.

This implies that;

N% = Speed Percentage = 12

N_{c} = Critical Speed = 10

MS = N% x N_{c}

MS = (^{12}/_{100}) x (10)

MS = (0.12) x (10)

MS = 1.2

Therefore, the **mill speed **is **1.2 m/s.**

**Calculating the Speed Percentage when the Mill Speed and the Critical Speed is Given.**

N% = ^{MS} / _{N}_{c}

Where;

N% = Speed Percentage

MS = Mill Speed

N_{c} = Critical Speed

Let’s solve an example;

Find the speed percentage when the mill speed is 24 and the critical speed is 6.

This implies that;

MS = Mill Speed = 24

N_{c} = Critical Speed = 6

N% = ^{MS} / _{N}_{c}

N% = ^{24} / _{6}

N% = 3

Therefore. the **speed percentage **is **3 m/s.**