The resting energy requirement: the calories a healthy dog at rest in a comfortable temperature needs in a day. The Merck Veterinary Manual gives it as 70 multiplied by the body weight in kilograms raised to the power 0.75. Everything else is a multiple of it.

Why is the answer a range and not one number?

Because both the Merck Veterinary Manual and WSAVA say an individual dog can need about 30% more or less than the formula predicts for its weight. A single number would look more precise than the science is. Start in the middle, then let the body condition score steer.

Should I just feed what the bag says?

The label is a fine starting point too — WSAVA names label recommendations and formulas side by side as starting points. Foods differ a lot in calories per cup, so the label for your food is what turns a calorie number into a scoop. If the two disagree badly, weigh the dog and re-score in a few weeks.

My dog is overweight. How many calories for weight loss?

This tool deliberately does not calculate that. A weight-loss plan is built from a target weight a vet sets after examining the dog, and the Merck Veterinary Manual warns that restricting an ordinary maintenance food can leave the dog short of nutrients as well as calories. Ask your vet about a plan and, often, a food made for it.

Do senior dogs need fewer calories?

Often, in practice, and the Merck Veterinary Manual says the adult years should not be treated as one stage. But the table it publishes has no separate senior multiplier, so we do not invent one. We estimate a senior on the adult rows and let the body condition score do the adjusting.

Tools

How many calories does my dog need?

A starting range from the published formula, checked against your dog's body condition. Not a diet plan.

Estimate the calories

Your dog's weight today

Life stage

Merck: 1.6 neutered, 1.8 intact

Neutered or spayed?

Activity

Merck's MER assumes a moderately active dog

Body condition score: 5 of 9

Ribs felt without excess fat over them; waist visible behind the ribs from above; tummy tucked up from the side. All nine scores

Enter a weight between about 1 and 240 pounds (0.5 to 110 kg) and the estimate appears here. The formula and every multiplier are printed below, so you can check it by hand.

Nothing you enter here leaves your browser. This is an estimate for a healthy dog, not a prescription — a dog with a medical condition, a pregnant or nursing dog, or a dog on a weight-loss plan needs its number from a vet.

The formula, and where every multiplier comes from

RER = 70 × (weight in kg)^0.75. The daily figure the tool shows is RER times one of the factors below, with a ±30% band around it. We chose which row each option maps to; we changed no number.

Energy multipliers used by the calculator
Dog	Daily need	Source
Puppy under four months	3 × RER	Merck Veterinary Manual
Puppy from four months to adult size	2 × RER	Merck Veterinary Manual
Adult, intact	1.8 × RER	Merck Veterinary Manual
Adult, neutered or spayed	1.6 × RER	Merck Veterinary Manual
Adult, obesity prone (our 'low activity' option)	1.4 × RER	Merck Veterinary Manual
Working or very active adult	about 2 × RER	Mullis et al., PeerJ 2015 (twenty working detection dogs)
Senior	the adult rows	No separate factor is published in the Merck table

Worked example: a neutered adult of 20 kg (about 44 lb) has an RER of 662 kcal. Times 1.6 is 1059 kcal a day, and the ±30% band runs from 741 to 1377. If that dog scores 5 of 9 and holds its weight, the food is right, whatever the arithmetic said.

Body condition score: the check on the arithmetic

WSAVA's nine-point scale scores fat by sight and touch: feel the ribs, look down on the waist, look at the tummy from the side. Four and five are ideal. WSAVA flags any score below 4 or above 5 for a fuller nutritional assessment — which is why this tool gives a maintenance estimate only, and sends anything outside the ideal band to a vet. Paraphrased from the WSAVA chart:

The WSAVA nine-point body condition score for dogs
Score	Group	What you see and feel
1	Under ideal	Ribs, spine and hip bones visible from a distance; no body fat you can find; obvious muscle loss.
2	Under ideal	Ribs, spine and hip bones easily seen; no fat to feel; some muscle loss.
3	Under ideal	Ribs felt easily and may be visible with no fat over them; tops of the spine visible; very obvious waist and tuck.
4	Ideal	Ribs easy to feel under a thin layer of fat; waist easy to see from above; tummy tucked up.
5	Ideal	Ribs felt without excess fat over them; waist visible behind the ribs from above; tummy tucked up from the side.
6	Over ideal	Ribs felt under a slight excess of fat; waist visible from above but not prominent; tuck still there.
7	Over ideal	Ribs hard to feel under heavy fat; fat over the lower back and base of the tail; waist barely visible or gone.
8	Over ideal	Ribs only felt with firm pressure, if at all; heavy fat over the back and tail base; no waist, no tuck.
9	Over ideal	Heavy fat over the chest, spine and tail base, and on the neck and legs; no waist; obviously distended belly.

Where this tool stops

We are not veterinarians and this is not veterinary advice. The estimate is for a healthy dog. Weight loss, weight gain after an illness, pregnancy and nursing, kidney, liver or gut disease, and any unexplained change in weight are conversations with your vet, who can examine the dog and set a target weight. The senior stage page and the puppy growth guide cover what changes at each end of life.

Questions people ask next

What is RER?: The resting energy requirement: the calories a healthy dog at rest in a comfortable temperature needs in a day. The Merck Veterinary Manual gives it as 70 multiplied by the body weight in kilograms raised to the power 0.75. Everything else is a multiple of it.
Why is the answer a range and not one number?: Because both the Merck Veterinary Manual and WSAVA say an individual dog can need about 30% more or less than the formula predicts for its weight. A single number would look more precise than the science is. Start in the middle, then let the body condition score steer.
Should I just feed what the bag says?: The label is a fine starting point too — WSAVA names label recommendations and formulas side by side as starting points. Foods differ a lot in calories per cup, so the label for your food is what turns a calorie number into a scoop. If the two disagree badly, weigh the dog and re-score in a few weeks.
My dog is overweight. How many calories for weight loss?: This tool deliberately does not calculate that. A weight-loss plan is built from a target weight a vet sets after examining the dog, and the Merck Veterinary Manual warns that restricting an ordinary maintenance food can leave the dog short of nutrients as well as calories. Ask your vet about a plan and, often, a food made for it.
Do senior dogs need fewer calories?: Often, in practice, and the Merck Veterinary Manual says the adult years should not be treated as one stage. But the table it publishes has no separate senior multiplier, so we do not invent one. We estimate a senior on the adult rows and let the body condition score do the adjusting.

Sources

Merck Veterinary Manual — Nutritional Requirements of Small Animals — RER = 70 × kg^0.75; the MER table (intact adult 1.8, neutered adult 1.6, obesity-prone 1.4, puppies 3 under four months and 2 over); MER assumes a moderately active dog; the ±30% individual variation; the warning about restricting a maintenance diet.
Merck Veterinary Manual — Table: Daily Maintenance Energy Requirements for Dogs and Cats — The multipliers themselves, as a standalone table.
WSAVA Global Nutrition Committee — Nutritional Assessment Guidelines (JSAP, 2011), PDF — Energy needs vary by about 30% either way in dogs; MER depends on body condition, neuter status, life stage and activity; a BCS below 4 or above 5, and treats above 10% of calories, flag a fuller assessment.
WSAVA — Body Condition Score chart for dogs (PDF) — The nine-point scale and its three groups, paraphrased in the table on this page.
Mullis, Witzel & Price — Maintenance energy requirements of working detection dogs (PeerJ, 2015) — The 'working or very active' row: twenty working dogs averaged about two times their calculated RER.

All opened and read on 2026-09-25.