Practical guide
Dog Food Dry Matter Comparison: Calculator, Worksheet and Limits
To convert an as-fed nutrient percentage, divide it by 100 minus the moisture percentage, then multiply by 100. When you use label minimums and maximums, record the result as a label-based estimate. It is not the exact composition, a proved dry-matter bound or a food-quality score.
Dog food dry-matter calculator for two foods
What changes when you remove water from the comparison?
An as-fed percentage includes the food's water in the denominator. A dry-matter percentage expresses the nutrient relative to the material left after excluding that water. Comparing the printed protein percentage on a can with the printed percentage on a dry bag therefore compares different moisture bases.
The FDA explains this conversion in its pet-food comparison guidance. With a moisture figure of 78%, the calculated dry matter is 22%. A stated 8% protein figure then gives 8 ÷ 22 × 100 = 36.36% on that calculation basis.
Picture 100 g of food containing 78 g of water and 8 g of protein, if those were its actual amounts. The remaining 22 g is dry matter; 8 of those 22 g is protein. The answer describes a fraction of the dry matter. It does not mean the original 100 g serving now contains 36.36 g of protein.
Labels usually supply guarantees rather than those exact amounts. The arithmetic is the same, but the interpretation changes. Keep the type of input beside the answer so that removing water does not also remove the qualification attached to the data.
Read the minimum and maximum words before entering numbers
AAFCO's label guidance describes the usual guarantees as minimum crude protein, minimum crude fat, maximum crude fiber and maximum moisture. “Crude” refers to the analytical method; it is not an ingredient-quality grade.
| Input on the package or report | What it states | What the calculator can show |
|---|---|---|
| Crude protein minimum | A lower guarantee for the as-fed nutrient percentage. | A label-based estimate when combined with maximum moisture. |
| Crude fat minimum | The usual label fat minimum; a low-fat claim can also have a maximum. | The ordinary minimum-row estimate. Check other guarantees separately. |
| Crude fiber maximum | An upper guarantee for the crude-fiber row. | A label-based estimate, rather than an exact fiber measurement. |
| Moisture maximum | An upper guarantee; actual moisture can be lower. | The denominator based on the stated maximum. |
| Matching as-fed analysis | Reported nutrient and moisture values; identify typical, averaged or batch-specific data. | A conversion of that supplied dataset, with its original limits. |
Use the same nutrient row in both foods. Crude protein and crude fat are different measurements. Keep a minimum row distinct from a maximum row, and check that a manufacturer's additional analysis is not already expressed as dry matter.
Why a protein minimum plus moisture maximum does not prove a dry-matter minimum
The usual label calculation combines two bounds as though they were one pair of values. Maximum moisture sets a minimum dry-matter fraction, but actual dry matter may be larger. Dividing a protein minimum by the smallest allowed dry-matter fraction does not prove a minimum for the actual ratio.
A counterexample using an invented label
Label: protein minimum 8%; moisture maximum 78%. Label-based calculation: 8 ÷ 22 × 100 = 36.36%.
Suppose actual as-fed protein is 8% and actual moisture is 75%. These figures satisfy those two guarantees. Actual dry matter would be 25%, giving 8 ÷ 25 × 100 = 32%.
That permitted example is below 36.36%. The label calculation therefore cannot be described as “at least 36.36% actual dry-matter protein.” It is not proof of the exact composition either.
This is an original mathematical example, not a measured dog food or an allegation about a manufacturer's label. It explains why this worksheet calls the guarantee-based answer a label-based estimate, even though the formula itself is straightforward.
For crude fiber, the nutrient maximum and moisture maximum still do not tell you the exact amount. Avoid treating an approximate comparison as a clinical limit. Request the data your veterinarian needs when a diet decision depends on a nutrient restriction.
Three worked comparisons with the input basis visible
All numbers below are invented to demonstrate arithmetic and interpretation. They are not product tests, recommendations or nutrient targets for a dog.
Example 1: Two label guarantees
Food A: minimum protein 8%, maximum moisture 78%. Dry matter = 100 − 78 = 22%. Label-based estimate = 8 ÷ 22 × 100 = 36.36%.
Food B: minimum protein 24%, maximum moisture 10%. Dry matter = 100 − 10 = 90%. Label-based estimate = 24 ÷ 90 × 100 = 26.67%.
The larger estimate is A, even though its printed as-fed protein minimum is smaller. This demonstrates the moisture-basis change; it does not prove that A has more actual protein per serving or is the better diet.
Example 2: One moisture maximum, two possible compositions
Return to the minimum protein 8% and maximum moisture 78% label. Actual values of 8% protein and 78% moisture would convert to 36.36%; actual values of 8% protein and 75% moisture would convert to 32%.
Both pairs fit those two stated bounds. In the calculator, select supplied-analysis mode to calculate each hypothetical pair. The mode changes how the result is described; it does not turn invented numbers into a product analysis.
Example 3: Matching supplied as-fed analysis
Suppose a report gives Food A protein 12% and moisture 75%, on the same as-fed basis. Dry matter = 25%; conversion = 12 ÷ 25 × 100 = 48%.
Suppose the corresponding report for Food B gives protein 30% and moisture 8%. Dry matter = 92%; conversion = 30 ÷ 92 × 100 = 32.61%.
These results describe the supplied datasets. If the values are typical averages, retain that description. Averages do not establish the exact contents of every batch or serving.
Check units, existing dry-matter values and missing moisture
- Start with percentages by weight on the same as-fed basis. A value of 8 g per 100 g is 8%. A value in mg/kg needs a unit conversion first; 10,000 mg/kg equals 1%. A value in g per 1,000 kcal is a different basis and cannot go straight into this calculator.
- Do not convert a dry-matter value twice. If the report already says “dry matter” or “moisture-free,” keep that value on its stated basis. The tool expects as-fed inputs.
- Copy moisture for the exact product. Do not substitute a generic canned-food or kibble moisture number. Formulations and supplied data can differ.
- Keep data sources consistent. Do not silently combine an analysis nutrient value with a label moisture maximum and call the answer an actual composition.
- Stop when a required input is missing. Ask the manufacturer for matching nutrient and moisture information instead of filling the gap from a similar product.
The tool accepts moisture from 0% up to, but not including, 100%; a denominator of zero cannot be used. Nutrient inputs must be between 0% and 100%. It rejects unsupported text and hides an old result when an input changes.
In supplied-analysis mode, nutrient plus moisture cannot exceed 100%. In label mode, combining separate bounds can produce a nominal result above 100%; the tool flags it as unsuitable for describing actual composition. It does not declare the food impossible from those bounds alone. Recheck the basis and request matching data.
Use the answer alongside adequacy, calories and the actual question
Dry-matter conversion answers a moisture-basis question. It does not measure digestibility, amino-acid balance, ingredient quality, safety or individual tolerance. A larger protein percentage is not a nutritional score. The ingredient list is another type of information; one ingredient name does not establish the quality of the whole diet.
FDA guidance explains that the nutritional adequacy statement identifies a food intended as a complete and balanced diet, with life-stage distinctions. Treats, snacks and supplements are typically not intended as the sole diet. One converted nutrient row cannot replace that statement or demonstrate that every required nutrient is present in the appropriate amount.
A dry-matter percentage is also not a calorie value or a daily portion. For a shopping-cost question, use the matching cost per 1,000 calories calculator. For a nutrient amount relative to energy, obtain the relevant energy-based analysis rather than assuming two foods with similar dry-matter protein have the same protein per calorie.
If a medical condition, therapeutic diet or nutrient restriction drives the comparison, bring the labels and supplied analysis to your veterinarian. Use the calculator to make the data basis clear, rather than choosing or changing a medical diet from its results.
Save a comparison record and ask a specific data question
Download the editable comparison worksheet. Record the exact products, nutrient row, minimum/maximum wording, data source and conversion. Keep the adequacy statement separate from the arithmetic.
Food A label: minimum crude protein 8%; maximum moisture 78% Dry matter used: 22% Label-based estimate: 36.36% Interpretation: not an exact composition or proved actual minimum Missing data: matching typical as-fed protein and moisture Question: are both supplied analysis values for the same product and basis?
A useful manufacturer question is: “Can you provide typical as-fed crude protein, crude fat, crude fiber and moisture for this exact product, with the basis and date?” Ask for the specific additional data your veterinarian needs when a health question is involved. If the response is already on a dry-matter basis, record it that way.
Three checks before relying on a converted percentage
Use these original cases to check the denominator and the meaning of the inputs.
Case 1
A label states minimum protein 8% and maximum moisture 78%. Does 8 ÷ 22 × 100 prove at least 36.36% actual dry-matter protein?
Show answer and explanation for case 1
No. It is a label-based estimate from two bounds.
Actual protein 8% and moisture 75% would satisfy those bounds but give 8 ÷ 25 × 100 = 32%. Matching composition data are needed to describe actual composition.
Case 2
A manufacturer reports protein 30% on a dry-matter basis. Should you divide it again by 100 minus moisture?
Show answer and explanation for case 2
No. The value is already on a dry-matter basis.
The calculator expects as-fed inputs. Converting a dry-matter value again changes the meaning and can produce a misleading percentage.
Case 3
Two foods produce similar dry-matter protein percentages. Does that establish equal protein per calorie or equal nutritional quality?
Show answer and explanation for case 3
No. Neither conclusion follows from that percentage alone.
Protein per calorie needs an energy basis. Nutritional quality and suitability require information beyond a single nutrient ratio.
Sources and further reading
- FDA: Complete and Balanced Pet FoodAs-fed and dry-matter definitions, the conversion formula, and the separate nutritional adequacy and life-stage context. The original bound counterexample is our mathematical explanation, not FDA product-test data.
- AAFCO: Reading LabelsMinimum crude protein and crude fat, maximum crude fiber and moisture, the meaning of crude analytical methods and separate label fields. No guarantee is treated as an exact measurement.