What this calculator does
Moisture content compares how much of a sample's weight was water against how much was dry material, found by weighing it once as collected and again after drying it out completely. The result answers a simple practical question: how wet is this, expressed as a percentage rather than a weight.
The thing that trips people up is that there are two different, incompatible ways to calculate it. Wet basis divides the water lost by the original wet weight; dry basis divides it by the remaining dry weight instead. Agriculture, food science and soil testing almost always use wet basis, while wood, timber and composting more commonly use dry basis. The two numbers are never the same for a given sample, and mixing them up in a report or a contract can be a real problem, so this calculator shows both and lets you pick which one you need.
The formula
Subtract the dry weight from the wet weight to get the water lost during drying. For wet basis, divide that water weight by the original wet weight and multiply by 100. For dry basis, divide it by the remaining dry weight instead and multiply by 100. Both figures are shown so you can see how much they diverge for a given sample.
| Term | Meaning |
|---|---|
| Wet weight | The weight of the sample as collected, before any drying. |
| Dry weight | The weight of the same sample after it has been fully dried, with all free and bound moisture driven off. |
| Wet basis | Moisture content expressed as a share of the original wet weight: (wet − dry) ÷ wet × 100. |
| Dry basis | Moisture content expressed as a share of the remaining dry weight: (wet − dry) ÷ dry × 100. |
The inputs explained
| Field | What to enter |
|---|---|
| Wet weight (as-collected) (g) | The weight of the sample before drying, in any consistent unit. |
| Dry weight (after drying) (g) | The weight of the same sample after drying, in the same unit as the wet weight. |
| Basis | Which convention to report as the headline figure. Both figures are always shown underneath. |
When to use it
Grain, hay and produce (wet basis)
Agricultural buyers and moisture meters for grain, hay and fresh produce almost always quote wet basis, since it is the figure that determines storage risk and payment weight adjustments at the point of sale.
Timber and firewood (dry basis)
Wood moisture content is conventionally reported on a dry basis, which is why kiln-dried timber can show moisture readings that look unusually high if you mentally compare them to a wet-basis figure from another industry.
Comparing two lab reports
If one report states a moisture content and another states a different figure for what looks like the same sample, checking which basis each one used often resolves the apparent disagreement before assuming a measurement error.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How wet basis and dry basis diverge as a sample gets wetter
The same 100 g of dry material with increasing amounts of water added, showing both conventions side by side.
| Wet weight | Moisture content (wet basis) | Moisture content (dry basis) |
|---|---|---|
| 110 g | 9.09% | 10.00% |
| 120 g | 16.67% | 20.00% |
| 140 g | 28.57% | 40.00% |
| 160 g | 37.50% | 60.00% |
| 200 g | 50.00% | 100.00% |
| 300 g | 66.67% | 200.00% |
Questions
Which basis should I use?
Use whichever your industry, buyer or standard specifies. Agriculture, food and soil testing typically use wet basis; wood, timber and composting typically use dry basis. When in doubt, ask which one a contract or spec sheet expects, since the two numbers are not interchangeable.
Can dry basis moisture content exceed 100%?
Yes. Because dry basis divides by the smaller dry weight rather than the larger wet weight, a very wet sample can show a dry-basis moisture content well over 100%, which is normal for that convention and not an error.
What is the moisture content formula?
Wet basis is (wet weight − dry weight) ÷ wet weight × 100. Dry basis is (wet weight − dry weight) ÷ dry weight × 100. Both start from the same water-loss figure, they just divide by a different reference weight.
Why does the dry weight need to be from a fully dried sample?
If any moisture remains when the sample is weighed as "dry", the water-loss figure understates the true moisture content and both percentages will read low. Standard methods specify a drying temperature and time, or drying to a constant weight, to avoid this.
For converting an as-fed nutrient percentage onto a dry-matter basis using a known moisture content, see the dry matter basis conversion.