---
title: "Wood Moisture Content: the Number Behind Every Kiln Schedule"
description: "What MC actually means, why it is not the same as water weight, and how to use it for shipping, drying and inventory decisions."
image: "https://nestingcalc.com/og-default.png"
url: "https://nestingcalc.com/guides/wood-moisture-content-basics/"
locale: "en"
---

# Wood Moisture Content: the Number Behind Every Kiln Schedule

What MC actually means, why it is not the same as water weight, and how to use it for shipping, drying and inventory decisions.

## MC is water weight divided by dry wood weight

Moisture content on the oven-dry basis (the industry default) compares the water in a sample to the wood substance after oven-drying: MC\_od = (W\_wet − W\_od) / W\_od × 100. 100 g of oven-dry wood holding 50 g of water sits at 50% MC; 100 g of dry wood holding 150 g of water sits at 150% MC. The wet basis (common in soil science) divides by the wet mass instead — they are interchangeable, just do not mix them in the same calculation. The [Moisture content](https://nestingcalc.com/moisture-content-calculator/) tool accepts both and converts.

## Fresh tropical wood regularly exceeds 100% MC

Acacia mangium sapwood at 70–90% MC, eucalyptus 80–120%, and freshly felled pine sapwood 100–180% are routine. A cubic metre of acacia at 73% MC weighs 970 kg, but the dry wood inside is only 560 kg — the other 410 kg is water that will leave during drying. This is why shipping green timber by truck or container is dominated by water weight, not wood.

## MC drives the kiln schedule, not the calendar

Kiln operators start from the initial MC of the charge and run the schedule down to a target MC for the in-service climate. Typical targets: furniture for export 8–10% MC, US interior 6–10%, exterior joinery 12%, pallets 19%. The Drying mode of the [Moisture content](https://nestingcalc.com/moisture-content-calculator/) tool returns the final mass, the dry mass (which never changes), and the water mass lost — these are the three numbers you need to log for each charge.

## The dry mass is the constant

The Wood Handbook 2021 Eq. 4-2 (W₂ = W₁ × (100+MC₂)/(100+MC₁)) keeps the dry mass constant. 500 kg of wood at 60% MC contains 312.5 kg of dry wood; dried to 12% MC the same 312.5 kg of wood holds 37.5 kg of water, total 350 kg. A common online 'shortcut' uses the inverse ratio (1+MC₁)/(1+MC₂) and gives 714 kg — impossible. If your number goes up while drying, the formula is wrong.

## When in doubt, measure

Pin-style resistance meters are reliable between 6 and 30% MC; dielectric (pinless) meters work in 4–30% and are good for finished furniture but need species-and-temperature correction. Calibrate against an oven-dry sample (103 °C until constant mass, usually 24 h for 25 mm boards) at least once per species per kiln. The [Moisture content](https://nestingcalc.com/moisture-content-calculator/) tool handles the math; the meter and the kiln schedule handle reality.

[Moisture content](https://nestingcalc.com/moisture-content-calculator/) [Open the linear cutting calculator](https://nestingcalc.com/linear-cutting-calculator/)

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