How Much to Feed My Dog or Cat: Getting Portions Right

July 14, 2026 · FamilyPet+

One of the most common questions veterinarians hear is deceptively simple: "How much should I be feeding my pet?" The packaging has a chart, the internet has contradictory opinions, and your dog looks at you as though you have been starving him regardless of how much you put in the bowl.

The truth is that there is no single right answer — but there is a reliable method. Once you understand what drives your pet's energy needs, you can calculate a sensible starting portion, monitor how it affects body weight, and adjust accordingly. This guide walks you through that method step by step.

⚠️ Veterinary disclaimer: The feeding ranges and calculation methods in this article are for general educational purposes only. They do not replace personalized advice from a licensed veterinarian, who can account for your individual pet's health status, metabolic rate, and medical history. Always consult your vet before making significant changes to your pet's diet.

Why "Follow the Bag" Is Not Enough

Most pet food bags print a feeding guide based on body weight alone. This is a convenient starting point, but it systematically ignores several factors that can shift your pet's real caloric needs by 30% or more in either direction:

• Age — puppies and kittens have dramatically higher energy needs relative to their body weight than adult or senior animals.
• Neuter status — neutered pets generally have a lower resting metabolic rate than intact animals of the same weight, meaning the bag's recommendation may lead to gradual weight gain.
• Activity level — a working Border Collie and a retired Greyhound of the same weight are not the same animal metabolically.
• Physiological state — pregnancy and lactation dramatically increase caloric requirements; illness or recovery can suppress or elevate them.
• Body condition — a pet who is already overweight should be fed toward a target weight, not their current weight.

Bag charts are designed to prevent underfeeding across the widest possible population, which is why they frequently overshoot for sedentary or neutered pets.

The Key Factors That Determine Portion Size

Body Weight and Target Weight

The calculation starts from weight — but ideally from your pet's ideal target weight, not necessarily what the scale reads today. If your cat is 6 kg when she should be 4.5 kg, feeding her based on 6 kg will maintain the problem.

Ask your vet to assess body condition score (BCS) on a 9-point scale. A score of 4–5/9 is ideal for most cats and dogs. This score guides whether you should feed to current weight, a target weight, or something in between.

Age and Life Stage

Foods are formulated for life stages — puppy/kitten, adult, senior — and those labels matter. A kitten needs roughly two to three times the caloric density per kilogram of body weight compared to an adult cat. A senior dog often benefits from slightly fewer calories and more easily digestible protein.

Neuter Status

Neutering reduces energy requirements by roughly 20–30% in many animals. If you continue feeding the pre-neutering portion after the procedure, gradual weight gain is almost inevitable. This is one of the most common drivers of feline and canine obesity in household pets.

Activity Level

Think honestly about your dog's daily movement:

• A sedentary indoor cat or a small dog who gets two short walks per day is at the low end.
• An active adult dog with 60–90 minutes of vigorous exercise daily sits in the middle.
• Working dogs, sporting breeds in training, or very young animals in a growth phase sit at the high end.

Activity multipliers used in veterinary nutrition can shift daily caloric needs by 50% from the sedentary baseline.

How to Calculate a Starting Portion

Here is the method veterinary nutritionists generally use, simplified for everyday use.

Step 1: Estimate Resting Energy Requirements (RER)

The formula for RER in kilocalories per day is:

RER = 70 × (body weight in kg)^0.75

For a 10 kg adult dog: RER = 70 × (10)^0.75 ≈ 70 × 5.62 ≈ 394 kcal/day

Step 2: Apply a Life-Stage Multiplier

Multiply RER by a factor that reflects your pet's situation:

These ranges are illustrative. Your veterinarian can provide a multiplier tailored to your individual pet.

For the 10 kg neutered adult dog above, using 1.3: 394 × 1.3 ≈ 512 kcal/day

Step 3: Read the Label

Check the caloric content on your pet food's packaging. It is usually expressed as kcal per 100 g (dry matter), kcal per cup, or kcal per can. For example: 350 kcal per 100 g of dry kibble.

Divide your target daily kcal by the food's energy density:

512 kcal ÷ 3.5 kcal/g = approximately 146 g per day

Step 4: Weigh the Bowl

This is the step most people skip — and it is the most important. Cup measures are notoriously inaccurate (studies show errors of 20–80% depending on kibble density and how the cup is filled). A simple kitchen scale removes that variable entirely. Weigh the food before every meal, at least until you know exactly what your daily target looks like.

Step 5: Monitor and Adjust

A starting calculation is a hypothesis, not a verdict. Weigh your pet weekly for the first month. If they are gaining on a calorie-restricted plan, reduce by 5–10%. If they are losing when you want maintenance, increase. The goal is a stable weight at an ideal body condition score.

For cats, weight loss should be very gradual — no more than 0.5–1% of body weight per week — because rapid caloric restriction in cats can trigger hepatic lipidosis (fatty liver disease), a potentially serious condition.

Common Feeding Mistakes

Free-feeding dry kibble. Leaving a bowl full all day works for some cats, but it makes it nearly impossible to monitor intake or notice early appetite changes — one of the first signs of illness.

Ignoring treats in the calorie count. Treats should make up no more than 10% of daily caloric intake. A small biscuit for a cat can represent 5–10% of their daily budget. They add up fast.

Feeding by sight, not weight. "A handful" or "a scoop" will drift over weeks and months. Weigh the food.

Using the same portion across life stages. The portion that was right for your puppy at 6 months is not right at 18 months, and will not be right again at 7 years. Reassess at each life-stage transition and at every annual health check.

Sharing human food without accounting for it. Even small amounts of calorie-dense human food (cheese, meat trimmings) can meaningfully inflate daily intake for a small pet.

The Risk of Overweight

Obesity is one of the most prevalent preventable health problems in dogs and cats. It is associated with reduced life expectancy, increased risk of diabetes (particularly in cats), joint disease, respiratory issues, and certain cancers. Studies suggest that keeping a dog at a lean body weight can extend healthy lifespan by up to two years.

The problem is that weight gain happens slowly enough to be easy to miss — until it has already accumulated. This is why a regular weight log, reviewed alongside body condition assessments, is more useful than a single weigh-in at the annual check-up.

Tracking Portions and Weight Over Time

Keeping a feeding log — especially through life-stage transitions, after neutering, or when a pet is recovering from illness — takes the guesswork out of adjustments. Recording what you feed, when, and what the scale reads each week creates a clear picture of trends rather than a snapshot.

An app like FamilyPet+ includes a built-in NRC ration calculator alongside a daily tracking log for meals, water intake, and weight, so you can monitor how your pet responds to any portion adjustment over time — all in one place, accessible to everyone in the family.