How do Select the correct Yarn count fabric(S/jersey) GSM ?

How do Select the correct Yarn count fabric(S/jersey) GSM ?

Select the correct Yarn count for single jersey fabric:

Single Jersey 

Say, the require GSM is 160

Yarn count  = (-0.141) X (GSM) + 50.22

                   = (-0.141) X (160) + 50.22

                   = -22.58 + 50.22

                   = 27.66

So, to knit 160 gsm single jersey fabric we need yarn count 27.66/s