How to use this calculator
- Weigh the current sample. Record the current sample weight before oven drying or before target conditioning.
- Dry to constant weight. Enter the oven-dry sample weight after the sample no longer loses meaningful weight between checks.
- Set target moisture. Enter the desired service, conditioning or shop target moisture content.
- Scale to a batch. Enter a current batch weight if you want the same moisture estimate applied to boards, blanks or a stack.
How it works
Wood moisture content on the oven-dry basis is:
MC = (Wwet - Wod) / Wod x 100
where Wwet is the current sample weight and Wod is
the oven-dry wood weight.
The target sample weight at a desired moisture content is: Wtarget = Wod x (1 + MCtarget / 100) The water to remove is the current sample weight minus that target. A negative result means the sample is below target and would need to regain moisture.
The batch estimate first backs out dry wood mass from the current batch weight: Wbatch_od = Wbatch / (1 + MC / 100) then applies the same target-weight equation to the batch. After measuring moisture, use the wood movement calculator for width change, the lumber weight calculator for payload, and the cut list calculator when those boards become parts.
Worked example
Verified against the live calculator
A sample that weighs 100 g before drying and
88 g oven-dry has 12 g of water. Moisture content
is 12 / 88 x 100 = 13.6% MC. If the target is
8% MC, the target sample weight is 95.0 g, so the
sample needs to lose about 5.0 g of water.
Frequently asked questions
How do you calculate wood moisture content from weight?
On the oven-dry basis, moisture content is current sample weight minus oven-dry weight, divided by oven-dry weight, then multiplied by 100. The dry weight is the wood substance; the difference is water.
What is oven-dry basis moisture content?
Oven-dry basis means the water mass is compared with the oven-dry wood mass, not the current wet mass. Wood technology commonly reports MC this way, so a sample with 12 g water and 88 g oven-dry wood is 13.6% MC.
How do I find target weight at a desired moisture content?
Use target weight = oven-dry weight x (1 + target MC / 100). If the current sample is heavier than that target, the difference is water to remove. If it is lighter, the sample would need to regain moisture.
Does this replace a moisture meter?
No. This is an oven-dry weight calculation and target-weight screen. Pin and pinless moisture meters need their own species, temperature, depth and calibration corrections.
Method & assumptions
- Uses oven-dry basis moisture content, not wet-basis moisture content.
- Current sample weight must be greater than or equal to oven-dry sample weight.
- Batch scaling assumes the batch has the same moisture content as the measured sample.
- Does not model kiln schedules, drying stress, case hardening, checking, species correction, meter calibration, equilibrium moisture content, temperature correction or sampling error.