Written by Hazel, BVSc | April 2026
The most common question vets receive about dog nutrition isn’t ‘which food is best?’ It’s ‘how much should I feed?’ And the answer — maddeningly — is: it depends.
It depends on your dog’s weight, age, activity level, reproductive status, breed, and whether they have any health conditions. The feeding guides on the back of every dog food bag are deliberately conservative — they’re designed for ‘average’ dogs, which almost no dog actually is.
This guide gives you the actual tools — a vet-written formula, body condition scoring, and activity multipliers — to calculate the right amount for YOUR dog.
THE RER FORMULA: HOW VETS CALCULATE CALORIE NEEDS
RESTING ENERGY REQUIREMENT (RER):
RER = 70 × (body weight in kg) ^ 0.75
This formula calculates the calories your dog needs at complete rest — essentially, just to stay alive (breathing, circulation, body temperature).
EXAMPLE: For a 20kg dog:
RER = 70 × (20)^0.75 = 70 × 9.46 = 662 kcal/day
This is the baseline. Then multiply by an activity factor.
ACTIVITY MULTIPLIERS (applies to RER to get MER — Maintenance Energy Requirement):
- 1.2 — Desexed adult, inactive/indoor
- 1.4 — Intact adult, moderately active
- 1.6 — Active adult dog (daily vigorous exercise)
- 1.8 — Working/sporting dog
- 2.0–3.0 — Sled dog, competition dog
- 1.6–2.0 — Lactating female
- 3.0 — Puppy 0–4 months
- 2.5 — Puppy 4–12 months
- 1.8–2.2 — Adolescent 12–18 months
EXAMPLE CONTINUED: 20kg desexed moderately active dog:
MER = 662 × 1.4 = 927 kcal/day
Now check your food’s caloric density (kcal/cup or kcal/100g — on the bag or manufacturer website) to calculate cups/grams per day.
QUICK REFERENCE FEEDING TABLE
APPROXIMATE DAILY FOOD AMOUNTS (quality dry kibble, ~350–400 kcal/100g):
- 3kg dog (Chihuahua, Toy Poodle): 70–90g/day
- 5kg dog (Maltese, Shih Tzu): 100–130g/day
- 10kg dog (Beagle, Cocker Spaniel): 170–220g/day
- 15kg dog (Border Collie, Cattle Dog): 230–290g/day
- 20kg dog (Labrador mix, medium): 290–360g/day
- 25kg dog (Labrador, Staffy): 350–430g/day
- 30kg dog (GSD, Weimaraner): 400–500g/day
- 40kg dog (Rottweiler, Malinois): 510–640g/day
- 50kg dog (Great Dane, Bernese): 610–770g/day
IMPORTANT: These are starting estimates only. Monitor body condition score (see below) and adjust up or down by 5–10% every 2–4 weeks until ideal condition is reached.
BODY CONDITION SCORING: THE MOST IMPORTANT TOOL
Body condition score (BCS) is more accurate than any feeding guide for determining if your dog is eating the right amount.
BCS SCALE (1–9, ideal is 4–5):
- Ribs, spine, and hip bones visible without touching
- Severe muscle wasting
- Obvious waist and abdominal tuck
BCS 1–3 (UNDERWEIGHT):
→ Increase food 10–20%, vet check if no improvement
- Ribs easily felt but not visible
- Waist visible from above
- Slight abdominal tuck when viewed from side
- No obvious fat deposits
BCS 4–5 (IDEAL):
→ Current feeding amount is correct
- Ribs palpable but with slight fat covering
- Waist barely visible or absent
- Abdominal tuck minimal
BCS 6–7 (OVERWEIGHT):
→ Reduce food 10–15%, increase exercise
- Ribs cannot be felt under fat
- No waist definition
- Abdominal distension (hanging belly)
BCS 8–9 (OBESE):
→ Veterinary weight management programme required
HOW OFTEN: Assess BCS monthly at home. Vet check every 6–12 months with weight recorded.
TRANSITIONING TO NEW FOOD — THE RIGHT WAY
A sudden diet change causes gastrointestinal upset in most dogs: loose stools, flatulence, vomiting. This is not allergy — it’s the gut microbiome adjusting.
7-10 DAY TRANSITION SCHEDULE:
Day 1–3: 75% old food + 25% new food
Day 4–6: 50% old + 50% new
Day 7–9: 25% old + 75% new
Day 10: 100% new food
ADJUST SLOWER if: sensitive stomach, loose stools during transition, history of IBD or digestive disease
ADJUST FASTER if: switching away from a contaminated or recalled food, vet-directed dietary change for medical condition
ADDING PROBIOTICS: A probiotic supplement (Fortiflora, VetriScience) during the 10-day transition reduces GI upset significantly. Not essential but worthwhile for dogs with sensitive stomachs.
TREATS: THE HIDDEN CALORIE PROBLEM
Most dog owners dramatically underestimate how many calories their dog gets from treats. A medium-sized dog treat = 50–80 kcal. Three treats a day = 150–240 kcal — equivalent to 20–35% of their daily food allowance.
RULE: Treats should not exceed 10% of daily calorie intake. If you’re using food rewards for training, reduce the main meal proportionally.
LOW-CALORIE TREAT OPTIONS:
- Baby carrots: ~4 kcal each
- Green beans: ~5 kcal per piece
- Blueberries: ~3 kcal each
- Plain rice cake (small piece): ~15 kcal
- Small piece of cooked chicken: ~20–30 kcal
AVOID: Commercial treats marketed as ‘training treats’ that are 70–80% carbohydrate. Read labels.
FAQ
Should I feed my dog once or twice a day?
Twice daily is recommended for most adult dogs. Single daily feeding creates longer fasting periods (can trigger bile vomiting in some dogs) and doesn’t suit dogs prone to bloat. Puppies need 3 meals per day (4 meals for young pups under 12 weeks). Toy breeds need 3 meals per day to prevent hypoglycaemia.
Should I leave food out all day (free-feeding)?
Not recommended for most dogs. Free-feeding makes it impossible to monitor appetite changes (an early sign of illness), leads to obesity, and is incompatible with multi-pet households. Measure food and feed at set times.
How do I know if I’m feeding the right amount?
Monitor body condition score monthly. If ribs are easily palpable but not visible, waist is visible from above, and there is a slight abdominal tuck — your dog is at ideal weight. Adjust food up or down by 5–10% and reassess after 3–4 weeks.
My dog seems hungry all the time — should I feed more?
Not necessarily. Many breeds (Labradors especially) are genetically predisposed to always appearing hungry regardless of intake. A dog with an ideal BCS who begs constantly is not underfed — it is a behavioural response. Add bulk without calories: plain pumpkin (1–2 tbsp), green beans, or frozen plain carrot pieces.