$\therefore$ Loss in Wt. = W - W1

$\therefore$ Moisture % = $\frac{\text{loss in Weight}} {\text{Weight of coal sample}} \times 100 $ = $\frac{\text{W - W1}} {\text{W}} \times 100 $

Significance of Moisture:

1. It decreases calorific value of coal largely as it does not burn and takes away heat in the form of latent heat
2. It increases ignition point of coal Hence a coal with lower percentage of moisture is of better quality.