Dry matter basis, explained with real numbers

Dry matter basis is the nutrient level of a food with the water taken out. To get it, divide the label percentage by the food’s dry matter (100 minus the moisture percentage), then multiply by 100. It’s the only fair way to compare protein, fat or fiber between foods with different water content, such as kibble and canned food.

This is the second guide in our label series. If you haven’t read it, start with how to read a dog food label.

Why the label numbers mislead

The guaranteed analysis on a US label is given “as fed”, which means the water in the food is counted. Dry food is usually around 10% water. Canned food is often 75% to 82% water. Fresh and gently cooked foods sit somewhere in between, often around 60% to 75%.

Water has no protein, fat or fiber. So the more water a food contains, the lower every other percentage looks on the label, even if the food underneath is identical.

The formula

Two steps:

1. Dry matter % = 100 − moisture %
2. Nutrient on a dry matter basis = (nutrient % ÷ dry matter %) × 100

That’s all. You can do it on a phone calculator in the shop.

Worked example 1: a dry food

The label says:

• Crude protein (min) 24%
• Crude fat (min) 14%
• Crude fiber (max) 4%
• Moisture (max) 10%

Dry matter = 100 − 10 = 90%.

• Protein: 24 ÷ 90 × 100 = 26.7%
• Fat: 14 ÷ 90 × 100 = 15.6%
• Fiber: 4 ÷ 90 × 100 = 4.4%

For dry food the change is small, because there’s little water to remove.

Worked example 2: a canned food

The label says:

• Crude protein (min) 8%
• Crude fat (min) 5%
• Crude fiber (max) 1.5%
• Moisture (max) 78%

Dry matter = 100 − 78 = 22%.

• Protein: 8 ÷ 22 × 100 = 36.4%
• Fat: 5 ÷ 22 × 100 = 22.7%
• Fiber: 1.5 ÷ 22 × 100 = 6.8%

So the canned food, which looked like a third of the protein of the kibble on the label, actually has more protein once the water is removed: 36.4% against 26.7%.

Side by side

	Dry food, as fed	Dry food, dry matter	Canned food, as fed	Canned food, dry matter
Protein	24%	26.7%	8%	36.4%
Fat	14%	15.6%	5%	22.7%
Fiber	4%	4.4%	1.5%	6.8%
Moisture	10%	0%	78%	0%

Worked example 3: a fresh, refrigerated food

Fresh and gently cooked foods fall between kibble and cans. Say the label reads:

• Crude protein (min) 11%
• Crude fat (min) 7%
• Crude fiber (max) 1%
• Moisture (max) 70%

Dry matter = 100 − 70 = 30%.

• Protein: 11 ÷ 30 × 100 = 36.7%
• Fat: 7 ÷ 30 × 100 = 23.3%
• Fiber: 1 ÷ 30 × 100 = 3.3%

On the label, this food looks less than half as rich in protein as the kibble. On a dry matter basis it has more protein than the kibble and about the same as the canned food.

Common mistakes

Comparing as-fed numbers across formats. This is the mistake dry matter basis exists to fix. A “high-protein” kibble and a “low-protein” can may be the other way round once water is removed.

Using the wrong moisture figure. Use the moisture percentage from the guaranteed analysis on the same label. Don’t assume all dry foods are 10% or all cans are 78%. Some dry foods are 8%; some cans are 82%.

Subtracting instead of dividing. You can’t take the moisture away from the protein figure. Divide the nutrient by the dry matter percentage.

Comparing dry matter numbers with feeding amounts. Dry matter percentages describe the composition of the food. How much protein your dog actually eats in a day depends on how much food you feed, which depends on calories. That’s what the per-1,000-kcal method below solves.

Three limits to keep in mind

The label numbers are minimums and maximums, not exact values. Protein is a minimum, so the real figure may be higher. Moisture is a maximum, so the real figure may be lower. Dry matter math based on the guaranteed analysis is an estimate. Manufacturers can usually give you a “typical analysis” with average values, which is more precise.

Dry matter percentages ignore calories. Two foods with the same dry matter protein can differ in how much protein your dog actually eats per day, because a higher-fat food has more calories and you feed less of it. Vets and nutritionists often compare nutrients per 1,000 kcal for this reason. The WSAVA’s nutrition guidelines encourage owners to look beyond single label numbers and ask manufacturers for complete nutrient information.

More protein isn’t automatically better. Dry matter basis tells you how foods compare. It doesn’t tell you what your dog needs. That depends on age, health and activity, and is a conversation for your vet.

Converting to “per 1,000 kcal”

If you want the calorie-adjusted figure, you need the calorie statement from the label.

Nutrient grams per 1,000 kcal = (nutrient % as fed × 10) ÷ kcal per kg × 1,000

Example: the dry food above has 24% protein and 3,650 kcal per kg.

• 24% protein = 240 g of protein per kg of food
• 240 ÷ 3,650 × 1,000 = 65.8 g of protein per 1,000 kcal

This tells you how much protein your dog gets for each 1,000 calories it eats, whatever the food’s water content.

Let the tools do it

Our Compare tool converts every food in our database to dry matter basis automatically, so you can put a kibble, a canned food and a fresh food side by side. Product pages in the Food Finder show both the label values and the dry matter values.

Next in this series: how to spot hidden chicken in dog food.