You pick up a can of cat food and see 8% protein. Next to it, a bag of kibble shows 32%. It is natural to conclude that the kibble is four times richer, and that the can is a weak food. The conclusion is wrong, and it is the reason this question is one of the most common in pet nutrition. This guide explains where the gap comes from, shows the real comparison and gives you a way to read any label without being misled.
The short answer: it is the water
A pet food label shows nutrients as fed. The can is about three quarters water, so only about a quarter of what is in it is anything else. When the label says 8% protein, that is 8 grams of protein in 100 grams of wet food, and 100 grams contains around 78 grams of water. Dry kibble has about a tenth of that water, so the same 100 grams contains much more of everything that is not water, including protein.
It is as if you compared the sugar in a glass of orange juice with the sugar in a spoonful of jam. The jam is more concentrated by weight, yet the juice may have a great deal of sugar once you take the water into account. The comparison only makes sense when the water is removed.
Making the comparison fair
The method is to express each nutrient as a share of the dry matter, the food without its water. The formula, which our guide to dry matter basis explains in full, is:
dry matter protein % = label protein % ÷ (100 − moisture %) × 100
| Moisture | Label protein | Dry matter | Protein (DM) | |
|---|---|---|---|---|
| Wet food (can) | 78% | 8% | 22% | 36.4% |
| Wet food (pouch) | 82% | 9% | 18% | 50.0% |
| Kibble | 10% | 26% | 90% | 28.9% |
| Kibble (higher protein) | 8% | 32% | 92% | 34.8% |
Look at the first and last rows. The can looks at a quarter of the kibble’s protein on the label (8% against 32%), but on a dry matter basis it is slightly higher (36.4% against 34.8%). The Dry Matter Basis Calculator converts any label in one step.
Grams matter too: the amount you feed
The other side of the coin is how much you feed. A pet needs a certain amount of energy a day, and wet food has far fewer calories per gram than dry food. For a neutered 4 kg cat needing 238 kcal:
| Food | Energy | Grams a day | Protein as fed (g) | Protein from this food per day |
|---|---|---|---|---|
| Wet (can) | 1,000 kcal/kg | 238 g | 8% | 19 g |
| Kibble | 3,800 kcal/kg | 63 g | 32% | 20 g |
By grams of protein actually eaten each day, the two foods come out nearly the same. The wet food looks low on the label because the cat eats nearly four times as many grams of it. That is the second half of the explanation: label percentages are per 100 g of food, and a cat does not eat 100 g of each.
(These numbers describe typical foods and are only an illustration. Your own foods will differ, so read your labels.)
A worked example with a real decision
A cat owner is considering a switch from kibble to a wet food and worries that the wet food’s 8% protein is too little.
- Kibble: 32% protein, 8% moisture. Dry matter protein = 32 ÷ 92 × 100 = 34.8%.
- Wet food: 8% protein, 78% moisture. Dry matter protein = 8 ÷ 22 × 100 = 36.4%.
- The two are similar in concentration.
- The owner notes that the wet food has fewer calories per gram, so the amount rises from 63 g to 238 g a day for the same energy.
- The owner checks that the wet food is complete and balanced for the cat’s life stage, and talks to the vet about the switch.
The decision then rests on completeness, the cat’s health, preferences and cost, not on a misleading label percentage.
What else water does to a label
Protein is the example people notice, but every nutrient is diluted in the same way:
- Fat looks low in wet food. A wet food at 5% fat and 78% moisture is 22.7% fat on a dry matter basis.
- Fibre and ash look tiny.
- Calories per gram are much lower, which is why portions are larger.
- Minerals, listed as percentages, are also diluted.
So comparing any label percentage between a wet and a dry food, whether protein, fat, ash or fibre, needs the same correction.
What the calculation does not tell you
Even after the correction, the number is only a measure of concentration. It does not tell you whether:
- The food is complete and balanced for your pet’s life stage.
- The protein is digestible or of high quality.
- The food suits a pet with a medical condition, which may need more or less of certain nutrients.
- The food is good value, which depends on calories and price.
For these questions, check the label for a completeness statement and ask your vet.
Comparing cost fairly
A can that looks cheap per kilogram may be costly per calorie, and the reverse. The simple approach is to compare price per 1,000 kcal:
price per 1,000 kcal = bag price ÷ (bag kg × kcal per kg ÷ 1,000)
For example, a can of 85 g costing 0.90 with 85 kcal costs about 10.59 per 1,000 kcal, while a 3 kg bag of kibble at 30 with 3,800 kcal per kg holds 11,400 kcal and costs about 2.63 per 1,000 kcal. The Pet Food Price per 1,000 kcal Calculator compares two foods in one go. The calorie-based comparison is also the one that matches the amount a pet needs; see how this works for dogs in our guide to how many calories a dog needs.
Common mistakes
- Comparing label protein across wet and dry foods.
- Forgetting that wet food has fewer calories per gram.
- Calling a food weak because the can says 8%.
- Calling a food strong because the bag says 32%.
- Using a dry matter number to judge quality.
- Ignoring the moisture figure when it is missing from the label.
More examples: dog and cat foods side by side
| Food | Moisture | Protein as fed | Protein (DM) | Calories per gram (typical) | Grams for a 4 kg cat (238 kcal) |
|---|---|---|---|---|---|
| Wet cat food (pâté) | 78% | 10% | 45.5% | 1.0 | 238 g |
| Wet cat food (chunks in jelly) | 82% | 8% | 44.4% | 0.8 | 298 g |
| Dry cat food (high protein) | 8% | 38% | 41.3% | 4.0 | 60 g |
| Dry cat food (standard) | 10% | 30% | 33.3% | 3.6 | 66 g |
| Semi-moist | 30% | 25% | 35.7% | 3.0 | 79 g |
The wet foods have the lowest label protein but the highest dry matter protein, and the cat eats three to four times as many grams of them. These are typical figures for illustration, and your own foods will differ, so use the label.
Why people are misled, and by what
Several habits make the label hard to read:
- Large print on the front. A claim of “high protein” may be true as a dry matter figure and not as fed.
- Percentages without units. A percentage alone says nothing about how much you feed.
- The “analysis” panel in small print. Moisture is often at the bottom, and easy to skip.
- Comparisons in adverts. Ads for one format may compare as-fed numbers across formats.
The remedy is to look for moisture on every label and convert before comparing.
Using the idea to compare your own foods
Take two foods you are considering and copy their numbers into a table.
| Food 1 | Food 2 | |
|---|---|---|
| Moisture | ||
| Protein as fed | ||
| Fat as fed | ||
| Dry matter (100 − moisture) | ||
| Protein (DM) | ||
| Fat (DM) | ||
| kcal per kg | ||
| Price per kg | ||
| Price per 1,000 kcal |
Filling it in takes five minutes and will tell you more than any advertisement. If you are comparing prescription diets, ask your vet to help, because their formulations may be set on a different basis.
Quick rule
To compare any two foods, put both on a dry matter basis first. Convert each nutrient by dividing the as-fed figure by (100 − moisture) and multiplying by 100. Only then say which food is higher in protein.
What dry matter does not tell you
A high dry matter protein figure does not prove a food is better. It does not tell you digestibility, ingredient quality, amino acid balance or whether the food is complete for your pet’s life stage. Check the nutritional adequacy statement on the label, which says whether the food is complete and balanced and for which stage, and ask your vet to help with choices for pets with health conditions.
Practical takeaways
Check moisture first, convert to dry matter, then compare. Remember that pets eat different weights of wet and dry foods for the same calories, so grams of protein per day can be compared too: multiply grams fed by the as-fed protein percentage. Finally, check the adequacy statement and ask your vet if your pet has a health condition that affects protein needs, such as kidney disease, where the right level is a medical decision.
Quick summary
- Labels show nutrients as fed, so wet food looks low in protein because it is mostly water.
- Convert with dry matter protein % = label % ÷ (100 − moisture %) × 100.
- A can at 78% moisture and 8% protein is 36.4% on a dry matter basis, above a kibble at 10% moisture and 26% protein (28.9%).
- Wet food has fewer calories per gram, so you feed more grams for the same energy.
- The number shows concentration, not quality; check completeness and ask your vet.
- Use the Dry Matter Basis Calculator and compare price per 1,000 kcal.
Frequently asked questions
Why does wet food have less protein than dry food on the label?
Because the label shows protein as a percentage of the food including water. Wet food is about three quarters water, so every nutrient percentage looks small.
Is wet food lower in protein than dry food?
Not necessarily. On a dry matter basis many wet foods are as high as or higher than kibble.
How much water is in wet food?
Often about 75 to 82%, but check the moisture figure on each label.
Should I choose a food by protein percentage?
Not by the label percentage alone. Compare on a dry matter basis, check that the food is complete and balanced for the life stage and follow your vet's advice.
Does more water mean fewer calories per gram?
Yes. Wet food has fewer calories per gram, so you feed more grams for the same calories.
How do I compare the cost of wet and dry food?
Use price per 1,000 kcal, which accounts for both water and calorie content.
Do the same rules apply to dogs and cats?
Yes. The arithmetic is the same for any pet food.
Sources
- WSAVA Global Nutrition Guidelines
- NRC (2006) Nutrient Requirements of Dogs and Cats, National Academies Press
- Pure arithmetic: dry matter nutrient % = label nutrient % ÷ (100 − moisture %) × 100
Related calculators
- Dry Matter Basis CalculatorCompare wet and dry pet foods fairly by removing the water from the label percentages.
- Pet Food Price per 1,000 kcal CalculatorCompare two foods fairly by price per 1,000 calories instead of price per bag.
- Pet Food Energy ConverterConvert pet food energy between kcal per kg, per 100 g, per pound and per ounce.
Keep reading
- Dry Matter Basis: Compare Wet and Dry FoodLearn how dry matter basis works, the formula to convert any pet food label, worked examples for wet, dry and semi-moist foods and common label traps.
- How to Calculate Protein on a Dry Matter BasisStep-by-step protein on a dry matter basis for dog and cat food: the formula, a conversion table for common moisture levels and worked examples.
- How Much Wet Food Should a Cat Eat a Day?How much wet food a cat needs a day: grams and cans by weight, how kcal per can works, mixing wet with dry and how to avoid overfeeding with pouches and tins.