BIZOMAT MAKEOS · Materials
Wood Moisture Content and Density
What is the moisture content of this timber, and what is its density at a given moisture content?
Moisture content of wood from its wet and oven-dry mass, and the density of wood at any moisture content from its specific gravity by the handbook formula, with the mass of a piece at that moisture content.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Mass as tested | g | Mass of the sample as received. |
| Oven-dry mass | g | Mass after oven drying to constant weight. |
| Specific gravity of the wood | Specific gravity of the species (oven-dry mass ÷ volume at the stated moisture, from wood property data). | |
| Moisture content for density | % | Moisture content at which density is wanted. |
| Volume of a piece | L | Volume of a piece for its mass. |
What each input means
Open an input to see what it is, its units, the worked example and the common mistakes, with a small diagram.
What this means: Mass as tested
- What it is
- The mass of the wood sample as received or tested, before any drying.
- Units and format
- Enter a number in g: grams. The form accepts 0.000001 g or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 12.5 g as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The moisture content rises with the difference between this and the oven-dry mass.
- Get it right
- Weigh the sample straight after cutting so it does not lose moisture first.
What this means: Oven-dry mass
- What it is
- The mass of the same sample after drying in an oven until its mass stops changing; it cannot exceed the tested mass.
- Units and format
- Enter a number in g: grams. The form accepts 0.000001 g or more. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 10 g as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Moisture content is the water mass divided by this dry mass, so it is on a dry basis and can exceed 100 %.
What this means: Specific gravity of the wood
- What it is
- The specific gravity of the wood species: oven-dry mass compared with the mass of an equal volume of water, from wood property data.
- Units and format
- Enter a plain number with no unit. The form accepts 0.05 to 1.5. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 0.5 as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Wood data quote specific gravity on different volume bases (green, oven-dry or at a stated moisture); check which basis your source uses.
What this means: Moisture content for density
- What it is
- The moisture content at which you want the density, as a percentage of oven-dry mass. It is separate from the sample result above and is not taken from it.
- Units and format
- Enter a number in %: percent: the number is read as a percentage, so type 8 for 8 %. The form accepts 0% to 300%. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 12% as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Get it right
- Type the percentage itself, not a fraction.
What this means: Volume of a piece
- What it is
- The volume of a piece of the same wood at the chosen moisture content, used to give its mass.
- Units and format
- Enter a number in L: litres. The form accepts 0.000001 L to 10000000 L. Required: the tool does not calculate until every input is valid.
- Example
- The form opens with 50 L as a worked example. It is an illustration, not a recommended value: replace it with your own figure.
- Effect on the result
- The mass of the piece rises in proportion.
Method and formulas
- Moisture content = (wet − oven-dry) ÷ oven-dry × 100%.
- Density ρ = 1000 G (1 + M ÷ 100) ÷ (1 + 0.009 G M) kg/m³ — the handbook’s 62.4 G (1 + M/100) ÷ (1 + G × 0.009 × M) lb/ft³.
- Example: 12.5 g drying to 10 g is 25% moisture; at 12% the wood weighs 531.31 kg/m³.
Limitations
- The density formula applies below fibre saturation, about 30% moisture.
- Specific gravity varies within a species; use measured values for weight-critical work.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check timber for crating, patterns or jigs before use
- Estimate the weight of timber at delivery moisture
- Track drying of seasoned stock
Who it is for
- Pattern makers
- Packaging and crating supervisors
- Buyers
What you get
- Moisture content of the sample
- Density at the moisture content
- Mass of the piece
Interpreting the result
- Timber for patterns and jigs should be dried close to the moisture it will live at to avoid movement.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 386–387, 3019. Topic reference; no source tables or recommended settings are reproduced.
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