Pet Food Portion Calculator
Feed the pet in front of you — weigh the food and adjust to body condition.
Work out how much to feed your dog or cat each day — grams of food and grams per meal — from bodyweight, life stage or goal and your food's energy. It uses the vet-standard energy method (RER then MER), so the number is tailored to your pet, not just the back of the bag.
Estimates from bodyweight, life stage and typical food energy — a planning guide only. Always follow your vet's advice and adjust to body condition.
How the daily amount is worked out
Energy first, then grams
Vets don't feed by weight, they feed by energy. First comes the Resting Energy Requirement — the calories an animal burns just existing: RER = 70 × bodyweight(kg)0.75 kcal/day. That resting figure is then scaled up by a life-stage factor to give the Maintenance (Daily) Energy Requirement, MER = RER × factor. Typical factors are about ×1.6 for a neutered adult dog and ×1.2 for a neutered adult cat, rising to ×2–3 for a growing puppy or kitten and higher again for hard-working dogs; for weight loss the RER is taken on the target weight and multiplied by about ×1.0 (dog) or ×0.8 (cat). Finally, calories become food: grams/day = MER × 100 ÷ the food's energy density (kcal/100 g). This is the WSAVA/AAHA global veterinary standard used in UK practice — the equation isn't country-specific, but the factor, your food's energy and the ideal weight all vary, so they're inputs.
Worked example
A neutered 20 kg dog: RER = 70 × 200.75 ≈ 662 kcal, then MER = 662 × 1.6 ≈ 1,059 kcal/day. On a typical dry food at 375 kcal/100 g that's 1,059 × 100 ÷ 375 ≈ 282 g of food a day — about 141 g per meal split over two meals. Switch to a wet food at ~90 kcal/100 g and the same dog needs roughly 1,177 g, because wet food is mostly water.
This is an estimate, not a prescription. Individual pets vary by breed, metabolism, health and neuter status. Weigh the food, watch the body condition score, and adjust every couple of weeks. Your vet's advice always overrides this tool — especially for puppies, kittens, pregnancy, illness or a weight-loss plan.
Why life stage changes the amount so much
The same bodyweight can need very different amounts of food depending on age, neuter status and how active the animal is. These are the typical MER factors applied to Resting Energy Requirement:
- Inactive / senior — ~×1.2–1.4. Older, quieter pets burn less; it's easy to keep feeding "adult" amounts and watch the weight creep on.
- Neutered adult — ~×1.6 dog, ×1.2 cat. Neutering lowers energy needs, so a neutered pet needs noticeably less than an entire one of the same weight. A 4 kg small dog lands at ≈317 kcal, about 84 g/day of 375 kcal/100 g dry food.
- Intact adult — ~×1.8 dog, ×1.4 cat. Entire animals run a little hotter.
- Active / working — ~×2–5 dog. A weekend agility dog sits near the bottom of that range; a full-time working or sled dog near the top. A 30 kg working dog at ×2.5 needs ≈2,243 kcal/day — roughly 598 g of dry food.
- Growth (under 4 months) — ~×3, then ~×2 (4–12 months). Puppies and kittens are building a body and need far more energy per kilo than adults. A 10 kg pup aged 4–12 months needs ≈787 kcal, about 197 g/day of a 400 kcal/100 g puppy food across three meals.
- Weight loss — RER on the target weight × ~1.0 dog / ×0.8 cat. A cat going from 5 kg to a 4 kg target works out at ≈42 g/day; a dog from 25 kg to 22 kg at ≈190 g/day. Weight gain for an underweight pet nudges the factor the other way.
Pick the row that matches your pet honestly — over-estimating activity is the most common way pets are quietly overfed. If your vet has given you a specific multiplier, enter it in the Detailed level to override the goal.
Food energy, reading the label and weighing portions
Dry vs wet — it's all about water
A typical dry food holds about 375 kcal per 100 g; a typical wet food only about 90 kcal per 100 g, because it's roughly three-quarters water. To reach the same daily calories your pet needs about four times the weight of wet food — a 5 kg cat needing 281 kcal eats about 75 g of dry food or about 312 g of wet, for identical energy. Always compare foods on calories, not grams.
Reading a UK pet-food label
UK and European labels state metabolisable energy as kcal per kilogram, and some give kcal per 100 g directly, in line with FEDIAF nutritional guidelines. This calculator wants kcal per 100 g, so divide the kcal/kg figure by 10 — a food listed at 3,750 kcal/kg is 375 kcal/100 g. Enter your own food's number for the most accurate result: the figure varies a lot between products — dry roughly 300–450 and wet roughly 70–130 kcal/100 g — so premium and "light" foods can sit well above or below the defaults.
Weigh it, don't scoop it
Kitchen scales beat a measuring cup: studies have found cups can be out by 20–50%. Weigh the daily amount once, note where it sits in your scoop, and keep treats under about 10% of daily calories — treats count, and they add up fast. Then let the body condition score, not the bowl, be the final word: you should feel the ribs easily with a light cover, and see a waist from above.
❓ Frequently asked Frequently asked questions
How much should I feed my dog?
It depends on weight, life stage and activity, not just a number on the bag. Vets use the animal's Resting Energy Requirement — RER = 70 × bodyweight(kg)^0.75 kcal/day — then multiply by a life-stage factor: about 1.6 for a neutered adult, 1.8 for an intact adult, up to 2.0 or more for a working dog, and 2–3 for a growing puppy. A neutered 20 kg dog has an RER of about 662 kcal, so it needs roughly 1,059 kcal a day, which is about 282 g of a typical dry food at 375 kcal/100 g. Split it across two meals — about 141 g each — and adjust up or down every couple of weeks to keep a lean body condition.
How much should I feed my cat?
Cats need far fewer calories than their size suggests. Using RER = 70 × weight^0.75, a 5 kg cat has a resting need of about 234 kcal; with a factor of about 1.2 for a neutered indoor adult that gives roughly 281 kcal/day. On a dry food at 375 kcal/100 g that's only about 75 g — a small amount that's easy to overfeed. On a wet food at about 90 kcal/100 g the same 281 kcal is about 312 g. Growing kittens and pregnant or nursing queens need much more (a factor of 2–3). Weigh the food rather than free-pouring, and let body condition, not the bowl, guide the amount.
Why is the wet-food portion so much bigger than dry?
Because wet food is mostly water. A typical dry food packs about 375 kcal per 100 g, while wet food is only around 90 kcal per 100 g — roughly a quarter as dense. To hit the same daily calories your pet therefore needs about four times the weight of wet food: the 5 kg cat needing 281 kcal eats about 75 g of dry food or about 312 g of wet. The animal isn't eating more energy; it's eating more water. That's why the gram figure jumps when you switch the food type — always compare foods on calories, not grams.
How do I read the calories on a UK pet-food label?
UK and European labels state metabolisable energy as kcal per kilogram, and some give kcal per 100 g directly, in line with FEDIAF nutritional guidelines. This calculator asks for kcal per 100 g, so divide the kcal/kg figure by 10 — a food listed at 3,750 kcal/kg is 375 kcal/100 g. Once you have kcal/100 g, grams per day = daily calories × 100 ÷ energy density. The figure varies a lot between products (dry roughly 300–450, wet roughly 70–130 kcal/100 g), so always use your own bag's number rather than a generic one.
How do I feed my pet for weight loss?
Feed to the target (ideal) weight, not the current one, and go gently. A common vet approach bases the RER on the ideal weight and uses a factor of about 1.0 for dogs and 0.8 for cats. A cat now 5 kg but ideally 4 kg works out at about 158 kcal a day — roughly 42 g of dry food; a dog coming from 25 kg to a 22 kg target lands near 190 g/day, about a third less food. Keep treats under 10% of daily calories, weigh the food, and aim for slow loss — roughly 1–2% of bodyweight a week — with regular weigh-ins. Crash dieting is dangerous for cats in particular (risk of hepatic lipidosis), so always involve your vet in a weight-loss plan.
Where these figures come from
The method here is the mainstream veterinary-nutrition standard, not a country-specific rule. The energy equation and life-stage factors follow the WSAVA Global Nutrition Guidelines and AAHA feeding guidance used in UK practice; the food energy defaults are typical values you can replace with your own product's label figure.
- Resting Energy Requirement — RER = 70 × bodyweight(kg)^0.75 kcal/day (the standard allometric formula).
- Life-stage (MER) factors — neutered adult ~×1.6 (dog) / ×1.2 (cat); intact ~×1.8 / ×1.4; active/working ~×2–5; growth ~×3 then ~×2; weight loss RER on target weight ×~1.0 (dog) / ×0.8 (cat).
- Food energy density — typical dry food ~375 kcal/100 g, typical wet food ~90 kcal/100 g. UK and European labels state metabolisable energy as kcal/kg (some give kcal/100 g directly), in line with FEDIAF nutritional guidelines — divide kcal/kg by 10 for kcal/100 g.
- Treats — kept to ≤10% of daily calories, in line with standard veterinary advice.
Last checked: July 2026. This is a planning estimate, not veterinary advice. Individual needs vary with breed, health, metabolism and neuter status — weigh the food, monitor body condition, and follow your own vet's recommendation, especially for puppies, kittens, pregnancy, illness or weight loss.
Select the question that matches where you are right now.
The headline number is the estimated amount of food to feed per day — grams, plus grams per meal — to meet your pet's daily calories (MER) on the food you chose. The breakdown shows the resting and daily calories behind it and how much each meal works out to.
Use it as a starting point, weigh that amount, and split it across the meals you feed. Then check body condition every couple of weeks and nudge the amount up or down — the scales and the ribs are the real feedback, not the bowl.
It's not veterinary advice or a fixed prescription. It doesn't account for illness, pregnancy, medications or an individual dog or cat's metabolism. For puppies, kittens, weight loss or any medical condition, feed to your vet's plan.
Feeding by energy is how vets do it, because two foods of the same weight can differ hugely in calories. Enter your food's real kcal/100 g and the grams figure adjusts — a richer food means a smaller bowl.
Four things move the daily amount the most: bodyweight, life stage or goal, how active the pet is, and the food's energy density.
RER scales with weight to the power 0.75, and the life-stage factor can nearly double the result — a growing puppy needs far more per kilo than a neutered senior of the same weight.
Dry (~375 kcal/100 g) versus wet (~90) changes the grams roughly four-fold for the same calories. Always feed to your own food's label figure, not a generic gram amount.
Honest activity matters — over-rating it is the classic overfeeding trap. Treats should stay under ~10% of daily calories, and a weight-loss goal feeds to the target weight, not today's weight, so the amount deliberately comes down.
A few habits keep the portion honest and your pet in good shape.
Use kitchen scales — cups can be out by 20–50%. Weigh the daily amount once and mark the level on your scoop so the whole household feeds the same.
You should feel the ribs with a light cover and see a waist from above. If not, adjust by ~10% and re-check in two weeks — small, steady changes beat big swings.
Chews, training treats and table scraps are calories too. Keep them under 10% of the daily total and take that energy off the meals so the sums still add up.
Pet food is one line in the household budget. Model the wider cost of a pet and how it fits your monthly outgoings.
Life stage drives the feeding factor — check where your dog sits.
Dog age calculator →