For ease, you can purchase a string meter or any other string tension meter that measures it for you. All you need to do is clip it between the strings and it will read the number in the display.

If not, you can always use your hand and lightly tap the string bed to get an rough est.

The harder it is the higher the tension and vice versa.

there is a link. it tells u all the different strings. it also explains the string tension

the force apply on string it vibrate this vibration is called tension of the string

The tension of the string. Less tension = lower pitch. This can be achieved by loosening the string or lengthening the string.

apply the formula of tension