A dry matter calculator exists because feeds are bought, weighed and delivered wet, and animals use nutrients dry. A ton of silage at 62% moisture and a ton of hay at 12% moisture are not the same purchase, are not the same delivery, and cannot be compared on any nutrient figure until the water is taken out of both. This page performs that conversion in both directions: it turns an as-fed weight into the dry matter it actually contains, and it restates a nutrient percentage from an as-fed basis onto a dry matter basis so that two feeds can be set side by side honestly.
Arb Digital builds free calculators that show their working rather than hiding it behind a proprietary model. Everything on this page is a one-line conversion you could do on paper, which is exactly why it is worth having in a form: the arithmetic is trivial, the mistakes are not, and a percentage divided by the wrong number quietly wrecks every ration decision that follows it.
What This Dry Matter Calculator Does
Enter the weight of feed as delivered, the moisture content from the analysis report, a nutrient percentage on an as-fed basis, and the dry matter intake you are aiming to supply. The calculator returns the dry matter actually delivered by that weight, the dry matter percentage of the feed, the same nutrient restated on a dry matter basis, the as-fed weight that would be required to hit the target dry matter figure, and the sheer weight of water riding along in the delivery. Three bars show the dry matter and water split of the as-fed weight and how far the current delivery gets towards the target.
The unit selector changes the label only, because every one of these conversions is a ratio and therefore unit-free. Pounds in, pounds out. Kilograms in, kilograms out. What matters is that you do not mix the two inside a single calculation, which is a more common error than it sounds when a lab report is metric and a bunk scale is not.
How to Use It
- Enter the as-fed weight. This is the weight on the scale, water included — per head per day, per pen, or per load, whichever unit of delivery you are working in. Keep the target in the same unit.
- Enter moisture from the analysis. Read it from the report rather than estimating it. A five-point error in moisture moves the dry matter figure by five points, and every nutrient percentage moves with it.
- Enter one nutrient on an as-fed basis. Crude protein is the usual choice, but the conversion is identical for starch, fibre, fat or ash. Run the tool once per nutrient if you need several.
- Enter your target dry matter figure. The calculator back-solves the as-fed weight needed to deliver it, which is the number the person on the loader actually needs.
- Recalculate whenever moisture moves. Silage moisture changes through a pit and hay moisture changes with the weather, so a single conversion done in spring is not still true in autumn.
The Formula / How It's Calculated
Dry matter percentage is 100 − moisture percentage. Dry matter delivered is as-fed weight × dry matter percentage ÷ 100. Converting a nutrient from an as-fed basis to a dry matter basis is as-fed nutrient % ÷ (dry matter % ÷ 100), and going back the other way multiplies instead of divides. The as-fed weight required for a target dry matter intake is target ÷ (dry matter % ÷ 100). Water delivered is simply the as-fed weight minus the dry matter.
Worked through the values the page loads with: 55 lb of feed at 62% moisture has a dry matter content of 38%, so it delivers 55 × 0.38 = 20.9 lb of dry matter and 34.1 lb of water. A crude protein of 3.1% on an as-fed basis becomes 3.1 ÷ 0.38 = 8.16% on a dry matter basis, which is the figure that can be compared against any other feed. To deliver a 22 lb dry matter target you would need 22 ÷ 0.38 = 57.89 lb as fed, so the current 55 lb is meeting 95.0% of the target.
The University of Georgia extension bulletin on measuring the dry matter content of feeds gives the same relationship from the sample-drying side, expressing it as %DM = 100 − [(original weight − dry weight) ÷ original weight] × 100, and notes that converting a dry matter amount back to an as-fed quantity means dividing by the percent dry matter.
Why the Report Prints Two Columns
Feed analysis reports show nutrients on both an as-fed and a dry matter basis, and the second column is the one nutritionists work in. Mississippi State University's extension guide to interpreting forage and feed analysis reports gives two reasons: the animal uses nutrients on a dry matter basis, and comparing every feed on the same basis is what makes ration building possible at all. It also states the rule that catches people out — for any given sample, as-fed nutrient values are always smaller than dry matter values.
That last point is worth sitting with, because it explains a very common misreading. A pasture and a hay can look like completely different feeds when their protein is quoted as fed, and turn out to contain identical protein once the water is removed. The difference was never in the plant. It was in how much water each sample happened to be carrying on the day it was cut.
The Error That Costs the Most
The expensive mistake in this arithmetic is almost never the nutrient conversion. It is the moisture figure itself. Because dry matter is 100 minus moisture, an error in moisture passes straight through into the dry matter weight at full size, and then into every nutrient percentage on top of it. Assume 55% moisture on a silage that is really 65% and you will over-deliver dry matter by more than a fifth without a single number on the report being wrong.
This is why moisture is the figure worth re-measuring rather than carrying forward. It is also the reason on-farm dry-down methods exist at all: a lab result from a month ago describes the sample that was posted, not the face of the pit today. The UGA bulletin above describes the Koster tester and microwave methods for exactly this, both of which produce a number you can type straight into the moisture field here.
Where This Sits Against Our Other Feed Tools
Two boundaries are worth drawing. Our pet calorie calculator works in energy: it estimates a daily calorie figure for a companion animal from body weight and life-stage factors. This page never touches energy requirements and never says how much an animal should eat. It converts weights and percentages between moisture bases, and the target intake is a number you supply, not one it recommends. The two tools answer questions that do not overlap.
The other boundary is with our feed conversion ratio calculator, which measures performance after the fact — feed consumed against weight gained over a period. Dry matter conversion is the step that makes that ratio meaningful, because a feed conversion ratio quoted on an as-fed basis for a wet ration is not comparable to one quoted on a dry basis for a dry ration. Run the conversion here first, then take the dry matter figures into the ratio tool.
Comparing Two Feeds on Price
The same conversion answers a purchasing question that gets asked badly. A quoted price per ton is a price for water plus feed. Divide it by the dry matter fraction and you get a price per ton of dry matter, which is the only version of the number that can be compared across a wet feed and a dry one. A silage at $55 a ton at 62% moisture costs $55 ÷ 0.38 = $144.74 per ton of dry matter; a hay at $130 a ton at 12% moisture costs $130 ÷ 0.88 = $147.73. On the delivered price the silage looked less than half the cost. On the basis the animal actually uses, they are within 2% of each other.
You can run that comparison on this page directly by entering the price per ton in place of the as-fed weight and reading the "as-fed weight for target" line with a target of one ton. If you want the underlying arithmetic on its own, our percentage calculator and ratio calculator handle the general cases, and the weight converter deals with the metric-to-imperial step before any of this begins.
What This Page Deliberately Does Not Do
It does not formulate a ration, recommend an intake, or suggest what any species should be fed. Those decisions depend on class of stock, stage of production, forage quality, climate and a dozen other variables, and they are made by a qualified nutritionist or veterinarian working with the specific herd or flock. The benchmarks quoted anywhere on this page are cited to a university extension service and are given as published reference points, not as targets for your animals.
Arb Digital designs, builds and maintains free tool libraries that earn organic traffic, with every figure sourced and every claim checked before it publishes.
Browse All Free Tools Talk To Arb DigitalCommon Mistakes to Avoid
- Multiplying when you should divide. Going from as-fed to dry matter basis divides by the dry matter fraction; going the other way multiplies. Reversing it on a 38% dry matter feed turns 3.1% protein into 1.18% instead of 8.16%.
- Comparing feeds on the as-fed column. Two forages with identical dry matter protein will look completely different as fed, purely because of moisture.
- Carrying an old moisture figure forward. Silage moisture varies through a pit and hay changes with storage, so a stale lab result silently distorts every calculation built on it.
- Mixing units inside one calculation. A metric analysis and an imperial scale will produce a plausible-looking answer that is wrong by a factor of 2.2.
- Treating a published benchmark as a target. Extension figures describe what was measured in a study population, not what your animals should be fed.
Related Free Tools From Arb Digital
Take the dry matter figures from this page into the feed conversion ratio calculator for performance arithmetic, or the crop yield calculator for the production side of a forage crop. For the underlying maths, the percentage calculator, ratio calculator and weight converter cover the general cases, and the concentration converter handles the equivalent problem in solution chemistry. Browse the full free online tools hub for the rest.
Frequently Asked Questions
Dry matter is what is left of a feed once all the water has been removed. Dry matter percentage is 100 minus the moisture percentage, so a feed at 62% moisture has a dry matter content of 38%.
Divide the as-fed percentage by the dry matter fraction. A crude protein of 3.1% as fed on a feed that is 38% dry matter becomes 3.1 divided by 0.38, or 8.16%, on a dry matter basis. To go back the other way, multiply instead.
Because the water in the sample dilutes every percentage on the as-fed column. Removing it concentrates the same quantity of nutrient into a smaller total weight, so the percentage rises. Mississippi State University's extension guide states this directly: as-fed nutrient values are always smaller than dry matter values for the same sample.
Divide the target by the dry matter fraction. A 22 lb dry matter target from a feed at 38% dry matter needs 22 divided by 0.38, which is 57.89 lb as fed.
No. Every conversion on this page is a ratio, so pounds in gives pounds out and kilograms in gives kilograms out. The unit selector changes the label only. The one thing that matters is not mixing units inside a single calculation.
Yes, on a price per unit of dry matter. Dividing a delivered price by the dry matter fraction gives the price of the feed the animal can actually use, which is the only basis on which a wet feed and a dry one can be compared fairly.
No. It converts between moisture bases and back-solves an as-fed weight for a target you supply. It sets no targets and makes no feeding recommendations, which are decisions for a qualified nutritionist or veterinarian working with your specific animals.
This calculator performs unit conversions only. It provides no feeding, nutritional, or veterinary guidance, and ration decisions for any animal should be made with a qualified animal nutritionist or veterinarian.
