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# Moisture Content Calculation

Moisture content is the amount of water present in a moist sample of a product like wood, soil or similar. Moisture content  can be be expressed on wet or dry basis.

### Moisture Content on Dry Basis

Moisture content on dry basis is the mass of water to the mass of dry solid:

MCd = mh2o / md                                        (1)

where

MCd = moisture content on dry basis

mh2o = mass of water (kg, lb)

md = mass of dry solid (kg, lb)

Moisture content on dry basis is commonly used in the timber industry. Note that it is common to multiply values with 100%.

### Water Content on Wet Basis

Water content on wet basis is the mass of water to the mass of water and mass of solid:

MCw = mh2o / m

=  mh2o / mh2o + md                                   (2)

where

MCw = moisture content on wet basis

mh2o = mass of water (kg, lb)

mw = total mass of moist - or wet - sample - mass of solid and mass of water (kg,lb)

### Example - Water Content in Birch on Wet Basis

The density of air-dried seasoned dry Birch is 705 kg/m3 with 20% (0.2) water content. The amount of water per unit volume can be calculated by transforming (2) to

mh2o = mw MCw

= (705 kg/m3) (0.2)

= 141 kg/m3

The amount of solids can be calculated as

md = (705 kg/m3) (1 - 0.2)

= 564 kg/m3

### Example - Moisture Content in Birch on Dry Basis

The density of air-dried seasoned dry Birch is 705 kg/m3 with 20% (0.2) moisture content. Equation (1) can be modified to

MCd = mh2o / (m - mh2o)                                  (1b)

where

m = mass  water and solid (kg, lb)

This equation can be transformed to

mh2o = MCd m / (1 + MCd )                  (1c)

The moisture content per unit volume can be calculated as

mh2o = (0.2) (705 kg/m3) / (1 + (0.2))

= 117.5 kg/m3

The amount of solids can be calculated as

md = m - mh2o

= (705 kg/m3) - (117.5 kg/m3)

= 587.5 kg/m3

## Related Topics

### • Material Properties

Material properties of gases, fluids and solids - densities, specific heats, viscosities and more.

## Related Documents

### Air - Drying Force

The drying force of air depends on the air moisture holding capacity and the water surface to air evaporation capacity.

### Air - Humidity Ratio

The mass of water vapor present in moist air - to the mass of dry air.

### Air - Moisture Holding Capacity vs. Temperature

The moisture holding capacity of air increases with temperature.

### Compressed Air - Water Content

Saturation pressure and maximum water content in compressed air.

### Fruits and Vegetables - Optimal Storage Conditions

Optimal temperature and humidity conditions for common fruits and vegetables.

### Soil - Water Content

Water or moisture content in soil.

### Water Content in Food and other Products

Water content before and after drying - in food and other products cork, grain, soap, peat, wood and more.

### Wood - Compressive Strength vs. Moisture Content

Red Spruce, Longleaf Pine and Douglas Fir - moisture content and their compressive strength.

### Wood Species - Moisture Content and Weight

Weight of green and air-dried fire wood.

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