Dry Matter Calculator (as-fed ↔ dry-matter basis for feed nutrients and amounts)

Understanding the dry matter calculator — concept and principle

Feeds contain very different amounts of water: silage is much wetter than hay. To compare them fairly, nutrients are expressed on a dry-matter (DM) basis. This calculator converts nutrient contents and feed amounts between as-fed and dry-matter bases.

Removing the water doubles the share: 2 kg of nutrient is 10% of the wet feed but 20% of its dry matter.

How it is calculated

With DM written as a fraction (50% = 0.50):

Nutrient on DM basis = nutrient as fed ÷ DM.
Nutrient as fed = nutrient on DM basis × DM.
Dry matter amount = amount as fed × DM; amount as fed = dry matter ÷ DM.
Water = as-fed amount − dry matter; nutrient amount = dry matter × DM-basis content.

The principle

Water carries no nutrients or energy, but it adds weight. A wet feed looks low in protein per kilogram simply because much of each kilogram is water. Removing the water from the calculation puts all feeds on the same basis, so they can be compared and rations balanced. Animal requirements are usually stated on a dry-matter basis for the same reason.

Worked example

Default inputs: DM 50%, crude protein 10% as fed, 20 kg of feed as fed.

Protein on DM basis = 10 ÷ 0.50 = 20%; as-fed value stays 10%.
Dry matter in 20 kg = 20 × 0.50 = 10 kg; feed amount as fed = 20 kg.
Water = 20 − 10 = 10 kg.
Protein in that feed = 10 kg × 20% = 2 kg.

How to read the result

Compare feeds by their DM-basis values; then use the as-fed amount to know how much to put in front of the animal. When a feed's moisture changes, for example silage after rain, the as-fed amount must change to keep the same dry matter intake.

Common mistakes

Comparing a DM-basis value from one lab report with an as-fed value from another.
Using DM as 50 instead of 0.50 in the formulas.
Forgetting to update DM when feed moisture changes.
Assuming hay and silage of the same crop have the same as-fed nutrients.

Keep in mind: Use lab-tested DM and nutrient values for ration formulation, and consult a nutritionist or veterinarian for animal diets.

Frequently asked questions

What is dry matter in feed?

What remains after all the water is removed; it contains all the nutrients.

How do I convert as-fed to dry-matter basis?

Divide the as-fed value by the DM fraction.

Why use a dry-matter basis?

It removes the effect of water so feeds can be compared fairly.

Sources: National Research Council (NRC/NASEM), Nutrient Requirements of Dairy Cattle (dry matter basis) · AOAC Official Method 934.01, Moisture in Animal Feed

Checked 9 Nov 2026. Reiling B., “Feed Dry Matter Conversions”, NebGuide G2093, University of Nebraska–Lincoln Extension, revised October 2022: as-fed → DM basis divides by the DM fraction (10% CP at 50% DM = 20% CP DM basis); DM → as-fed multiplies (93% TDN × 0.74 = 68.8%); feed weight as fed × DM = dry matter (40 lb × 0.60 = 24 lb); dry matter ÷ DM = as fed (45 lb ÷ 0.87 = 51.72 lb).

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