A guaranteed analysis is the standardized nutritional breakdown printed on the label of pet food, livestock feed, or fertilizer. It lists key nutrients as minimum or maximum percentages, giving you a legally backed promise that the product contains at least (or no more than) what the label states. You’ll find it on nearly every bag of dog food, cattle feed, or garden fertilizer sold in the United States, and it’s required by law.
How It Works on Pet Food Labels
On pet food, the guaranteed analysis must include four core nutrients: crude protein (minimum %), crude fat (minimum %), crude fiber (maximum %), and moisture (maximum %). The word “crude” refers to the lab method used to measure these nutrients, not to quality. A minimum guarantee means the product must contain at least that much of the nutrient in every batch. A maximum guarantee means it must contain no more than that amount.
This distinction matters. If a bag of kibble lists 26% minimum crude protein, a state lab testing that product should never find less than 26%. Crude fat works the same way. Fiber and moisture are capped because too much of either dilutes the nutritional value of the food. Manufacturers can voluntarily add other guarantees beyond the required four, and many do. You’ll commonly see calcium, phosphorus, omega fatty acids, and glucosamine listed on premium brands.
The maximum moisture allowed on a standard pet food label is 78%. Products labeled as stew, gravy, sauce, broth, or juice can exceed that threshold because their recipes naturally contain more water. This is why a can of dog food “in gravy” may look dramatically different in guaranteed analysis from a dry kibble, even if the actual nutrition per serving is comparable.
Why the Numbers Aren’t Exact
A guaranteed analysis is not the same as a typical or average nutrient profile. Every batch of pet food or feed varies slightly because ingredient composition, mixing rates, and cooking temperatures fluctuate during manufacturing. A single lab result from one batch doesn’t capture that variation.
To set their label guarantees, responsible manufacturers test multiple batches and use statistical methods. If the results follow a normal bell curve, setting the minimum below the low end and the maximum above the high end (roughly two standard deviations from the average) means about 95% of all batches will fall within the guarantee. In practice, this means the actual protein in your pet’s food is almost always higher than the minimum listed, and the actual fiber is almost always lower than the maximum. The guaranteed analysis represents a floor and ceiling, not a precise reading.
Comparing Products: The Dry Matter Formula
Comparing a dry kibble to a canned food using guaranteed analysis numbers straight off the label is misleading because of the moisture difference. A canned food with 10% protein and 75% moisture looks far worse than a kibble with 26% protein and 10% moisture, but that gap shrinks considerably once you account for water content.
To make an accurate comparison, convert both products to a “dry matter basis.” The formula is simple: divide the nutrient percentage by the dry matter percentage (which is 100 minus the moisture percentage). For a canned food with 10% protein and 75% moisture, the dry matter is 25%. So: 10 ÷ 0.25 = 40% protein on a dry matter basis. For the kibble with 26% protein and 10% moisture: 26 ÷ 0.90 = about 29% protein on a dry matter basis. The canned food actually delivers more protein per unit of solid food, despite looking weaker on the label.
Livestock Feed Tags
Commercial livestock feed uses the same guaranteed analysis concept but typically requires more detail. A feed tag in California, for example, must list minimum crude protein, minimum crude fat, maximum crude fiber, and maximum ash. If the ash content exceeds 9%, the label must also guarantee minimum and maximum calcium, minimum phosphorus, and maximum sodium or salt.
Vitamins and minerals get their own units. Vitamins A, D, and E are listed in International Units per pound (IU/lb). Amino acids like lysine appear as minimum percentages. Selenium, because it’s toxic in small excess amounts, must show both a minimum and maximum in parts per million whenever more than 0.3 ppm of added selenium is present. These extra requirements reflect the tighter nutritional management needed in livestock production, where feed efficiency and animal health have direct economic consequences.
Calcium and Phosphorus Ratios
One detail worth understanding on feed labels is the relationship between calcium and phosphorus. The National Research Council recommends a calcium-to-phosphorus ratio of 1.2 to 1 for dogs, though growing puppies may need ratios as high as 2 to 1 during peak growth between two and four months of age. A ratio around 1.4 to 1 is generally considered a safe target throughout a dog’s growth period. These numbers matter because an imbalance between the two minerals can interfere with bone development, particularly in large-breed puppies.
Fertilizer Guaranteed Analysis
On a bag of fertilizer, the guaranteed analysis appears as three bold numbers separated by dashes, like 18-4-10. These represent the percentage by weight of nitrogen (N), phosphorus as phosphate, and potassium as potash, in that order. A 50-pound bag of 18-4-10 fertilizer contains 9 pounds of nitrogen, 2 pounds of phosphate, and 5 pounds of potash.
Beyond the primary three, fertilizer labels may also list secondary nutrients like calcium, magnesium, and sulfur, as well as micronutrients like iron, manganese, and zinc, all expressed as percentages by weight. These additional disclosures are required whenever the manufacturer claims the product contains them. The guaranteed analysis on fertilizer serves the same legal function as on pet food: it’s a binding minimum that regulators can test and enforce.
How Labels Get Enforced
State departments of agriculture are responsible for verifying that guaranteed analysis claims are accurate. Inspectors pull product samples from store shelves, warehouses, or manufacturing facilities and send them to state laboratories for testing. In Oklahoma, for instance, the Department of Agriculture Laboratory is the only facility in the state authorized to perform label compliance testing for livestock feeds, pet foods, fertilizers, and liming materials.
Testing follows standardized methods from organizations like the Association of Official Analytical Chemists. If a product consistently fails to meet its label guarantees, the manufacturer faces penalties ranging from warning letters to fines to product removal. The nutrients listed in a guaranteed analysis must appear in the same units and order specified by the Association of American Feed Control Officials (AAFCO) for pet food, or by state fertilizer laws for plant nutrients. This standardization ensures you can compare products across brands using the same framework, which is the entire point of the requirement.
What Guaranteed Analysis Doesn’t Tell You
The guaranteed analysis reveals nutrient quantities but says nothing about nutrient quality or digestibility. Two dog foods can both list 26% minimum crude protein, yet one might use highly digestible chicken muscle while the other relies on plant-based protein concentrates that your dog absorbs less efficiently. The ingredient list, which appears separately on the label, gives you better insight into protein sources and overall formulation.
It also doesn’t tell you calorie content. AAFCO requires a separate calorie statement on pet food labels, expressed in kilocalories per kilogram and per familiar unit (cup, can, or pouch). And because guaranteed analysis values are expressed on an “as-fed” basis, meaning they include moisture, direct comparisons between wet and dry products require the dry matter conversion described above. Without that step, the numbers on the label can be genuinely misleading.