# About moisture contents (1) / sludge drying, slurry drying, waste drying

First, what is moisture contents?
In short, it is a ratio of the quantity of water contained in a material.However, there are two ways of expression for the ratio that are “mass ratio” and “volume ratio”.The expression of “mass ratio” is usually used.
The expression of “mass ratio” is usually used.In addition to that, there are actually two ways of referring “mass ratio”.They are “wet basis” and “dry basis” and difference between them is basis number used in their calculation. One uses mass of wet material for it and the other uses mass of dried material.

“Wet basis”
It suggests the quantity of water contained in a whole material. Normally, the following formula is used.
(Quantity of water / (Quantity of water + Quantity of a material) * 100
This is called wet basis and its unit is [%,W.B].

“Dry basis”
It suggests the quantity of water per a material in percentage. This formula is sometimes used for timbers.
(Quantity of water / Quantity of a material) * 100
This is called “dry basis” and unit is [%,D.B].
The maximum value may be much greater than 100 when this basis is used.

Conversion formula
The conversion formula between the two basis is the following.
Dry basis moisture contents
= (Wet basis moisture contents / (100 – wet basis moisture contents)) * 100
Wet basis moisture contents
= (dry basis moisture contents / (100 + dry basis moisture contents)) * 100

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