Reading Moisture and Energy Density on Cat and Dog Food Labels

Why moisture changes the numbers you see

Two pet foods can show very different protein or fat percentages simply because they contain different amounts of water. A canned food may appear lower in protein on its label than a dry food, even though that difference partly reflects dilution by moisture rather than a direct comparison of nutrient concentration.

To compare labels more meaningfully, start by identifying whether the figures are reported as-fed, convert nutrient percentages to a dry-matter basis when appropriate, and then consider energy density. These are comparison tools—not universal measures of food quality and not individualized feeding instructions.

How pet-food labels report moisture and nutrients

The guaranteed analysis is reported on an as-fed basis. In other words, the percentages describe the food as sold, including its water. Ingredient percentages are also listed by weight on an as-fed basis, so comparing these figures directly across food types can be misleading when moisture differs substantially.

For the guaranteed analysis, crude protein and crude fat are listed as minimums. Moisture and crude fibre are listed as maximums. These are label guarantees, not necessarily the product’s exact average composition. That distinction matters when using the figures in calculations.

• Crude protein: minimum value
• Crude fat: minimum value
• Moisture: maximum value
• Crude fibre: maximum value

Moisture differences by food type

Moisture varies substantially by product type. Dry foods contain about 3%–11% water, semimoist foods about 25%–35% water, and canned foods commonly contain 60% to more than 87% water. These are general, research-supported ranges rather than assumptions about a particular product. Always use the moisture value shown on the label when performing a comparison.

• Dry foods: about 3%–11% water
• Semimoist foods: about 25%–35% water
• Canned foods: commonly 60% to more than 87% water

How to convert an as-fed percentage to dry matter

The dry-matter calculation removes the mathematical effect of water. First subtract the moisture percentage from 100 to find the percentage of dry matter. Then divide the listed nutrient percentage by that dry-matter percentage and multiply by 100.

For example, imagine Food A lists 10% protein and 75% moisture. Its estimated dry-matter protein percentage is 10 ÷ (100 − 75) × 100, or 10 ÷ 25 × 100 = 40%.

Now imagine Food B lists 26% protein and 10% moisture. Its estimated dry-matter protein percentage is 26 ÷ (100 − 10) × 100, or 26 ÷ 90 × 100, which is approximately 28.9%. In this hypothetical example, Food A’s as-fed protein percentage looks lower, but its calculated dry-matter percentage is higher because Food A contains much more water. This is a demonstration of the calculation, not a ranking of foods.

• Nutrient percentage ÷ (100 − moisture percentage) × 100

Why the calculation has limits

Dry-matter calculations based only on a guaranteed-analysis moisture value are approximate. Moisture is listed as a maximum, so the actual amount may be lower. Protein and fat are also guaranteed minimums rather than exact average values. As a result, the calculation should not be presented as a precise measurement of what is in every serving.

When available, a manufacturer’s average nutrient profile may provide more informative comparison data than the guaranteed-analysis minimums and maximums. Even then, the figures should be interpreted as label information rather than a complete assessment of a food’s quality or suitability.

What energy density adds

Energy density adds another perspective. Metabolizable energy, or ME, is the energy value used for label calorie information. Pet-food labels commonly provide ME as kcal/kg. A label may also provide calories per a household unit such as a cup or can, but that value is directly available only when the manufacturer states it.

If only kcal/kg is provided, converting it to calories per cup, can, or another household unit requires the weight of that serving. Compare household-unit values directly only when the unit and serving definition are consistent across the foods being evaluated. Use the label’s stated value as the practical consumer comparison figure, while recognizing that manufacturers may not all use identical testing or estimation procedures.

• kcal/kg: kilocalories of metabolizable energy per kilogram
• kcal per cup, can, or another stated household unit, when provided
• Grams of a nutrient per 1,000 kcal

Comparing nutrients relative to calories

You can also compare nutrient supply relative to energy by calculating grams per 1,000 kcal. For example, if a food provides 80 grams of protein per kilogram and 4,000 kcal per kilogram, it provides 80 ÷ 4,000 × 1,000 = 20 grams of protein per 1,000 kcal. The same approach can be used for other listed nutrients when the necessary label or manufacturer average-profile information is available.

This method asks a different question from dry-matter analysis. Dry-matter percentage asks, “What proportion of the non-water portion is this nutrient?” Grams per 1,000 kcal asks, “How much of this nutrient is supplied alongside a given amount of energy?” Neither result replaces the other, and they should not be treated as interchangeable.

How to interpret the result responsibly

Energy density can help explain why different volumes of food may provide different amounts of energy. A less energy-dense diet may require a greater food volume to provide the same calories. However, energy density does not establish that a food is healthier, more complete, or universally preferable. Fewer calories do not automatically mean better nutrition.

Calorie needs vary with life stage and condition. This article does not calculate an individual dog’s or cat’s calorie requirement or recommend a feeding amount. Use label comparisons as educational context rather than as a personalized prescription.

A practical label-reading checklist and conclusion

A consistent worksheet can make label comparisons clearer. Begin with the as-fed values, then calculate dry matter for concentration comparisons. Separately record energy density and, when appropriate, nutrients per 1,000 kcal. Keeping these measures separate prevents a moisture comparison from being confused with a calorie-relative nutrient comparison.

The main lesson is simple: apparent percentages can change because water changes the denominator. Dry-matter calculations help remove that effect, while kcal-based measures add information about nutrient supply relative to energy. Together, they provide context for reading labels without ranking brands, prescribing portions, or treating a single label value as a complete definition of food quality.

• Record the food’s moisture percentage.
• Record crude protein and crude fat, noting that these are minimums.
• Record moisture and crude fibre, noting that these are maximums.
• Calculate dry-matter values when comparing nutrient concentration.
• Record kcal/kg and any stated kcal per cup, can, or other household unit.
• Where available, note whether the figures are guaranteed-analysis values or manufacturer averages.
• If useful, calculate grams of protein or fat per 1,000 kcal.
• Do not use one number alone to declare a food best or healthiest.