Dog Nutrition Glossary: RER, DER, AAFCO & Calorie Terms

July 18, 2026

The dog food calculator leans on a handful of specific veterinary nutrition terms. Here’s what each one means, in plain English.

RER (Resting Energy Requirement)

The number of calories a dog burns at complete rest, with no digestion or physical activity happening — essentially the metabolic cost of just being alive. Calculated as 70 × (body weight in kg)^0.75, RER is the baseline every other energy figure in the dog food calculator builds on. It scales with body weight using a 0.75 exponent rather than a straight 1:1 ratio, because metabolic rate rises more slowly than body mass as a dog gets bigger.

DER (Daily Energy Requirement)

RER multiplied by a life-stage and activity factor — the number that actually represents how many calories a specific dog needs in a day, accounting for growth, reproductive status, spay/neuter status, and activity level. DER is the figure the calculator’s portion size is ultimately based on. See the life-stage and activity multiplier table on the calculator page for the full range, from ×1.0 for weight loss up to ×5.0 for elite working dogs.

Metabolizable Energy (ME)

The amount of energy in food that’s actually available to the body after accounting for losses in digestion, absorption, and urine — as opposed to the food’s total (gross) energy content before those losses. AAFCO calorie statements on pet food labels are based on metabolizable energy, which is also what RER and DER are expressed in, so the units match up correctly when you divide DER by a food’s kcal/cup figure.

AAFCO Calorie Statement

A standardized statement AAFCO (the Association of American Feed Control Officials) requires on most complete and balanced pet food labels, expressed in kilocalories per kilogram of food “as fed,” and typically also per cup, can, or another familiar unit. According to AAFCO’s consumer guidance on reading labels, this statement is the label’s most reliable calorie-density source — see how to read a dog food label and find calorie density for exactly where to find it.

Calorie Density

How many calories a specific food packs into a given volume or weight — usually expressed as kcal per cup for dry food or kcal per can/kcal per 100g for wet or canned food. Calorie density varies substantially between brands, between dry and wet formulas of the same brand, and even between different recipes from the same manufacturer, which is why the dog food calculator asks for this number directly instead of assuming a default.

As-Fed vs. Dry Matter Basis

Two different ways of expressing a food’s nutrient or calorie content. “As-fed” reflects the food exactly as it comes out of the bag or can, moisture included — this is the basis AAFCO calorie statements use, and the basis the dog food calculator expects for its calorie-density input. “Dry matter basis” removes the water content mathematically, which is useful for comparing a wet food’s nutrient profile against a dry food’s on equal footing, but is a different figure and shouldn’t be entered into an as-fed calorie calculator by mistake.

Body Condition Score (BCS)

A standardized visual and hands-on assessment — commonly a 9-point scale — of how much body fat a dog is carrying, based on how easily ribs can be felt and whether a waist tuck is visible from above and the side. WSAVA’s official BCS chart places the ideal range at the middle of the scale, roughly a 4 or 5 out of 9. BCS is the real-world feedback loop meant to fine-tune whatever portion the calculator produces — see the pillar page’s body condition guidance for how to use it.

Life Stage

The broad developmental category a dog falls into — puppy, adult, or senior — each with meaningfully different energy needs per pound of body weight. The dog food calculator further splits puppies into a 0–4 month and a 4–12 month bracket because energy needs drop noticeably partway through the first year. For breed-specific puppy growth context alongside feeding, pair this with the puppy weight calculator.

Activity Multiplier

The factor DER multiplies RER by, ranging from ×1.0 for weight loss (calculated from ideal weight) up to ×5.0 for elite working or high-drive sporting dogs. Because the multiplier range is so wide for active or working dogs, the calculator uses an adjustable slider for those categories instead of one fixed number.

Free-Feeding

Leaving food available at all times rather than serving measured portions at set meals. Free-feeding makes it functionally impossible to know how many calories a dog is actually eating in a day, which is why it works against any portion figure a calculator like this one produces — see common dog feeding portion mistakes for more on why this undermines portion control specifically.

Ready to put these terms to work? Head back to the dog food calculator to get a starting daily portion, or see dog food portion examples by size and life stage for the math applied to real dogs.