Pet Food Calculator
Estimate daily calories, grams of food and grams per meal for a cat or dog from weight, life stage and activity.
Pet Food Calculator
Enter weight, life stage and activity level to estimate daily calories, grams of staple food and grams per meal for a cat or dog.
These numbers are estimates from a general formula, not a veterinary diagnosis. Body condition and veterinary advice come first; ask a veterinarian if your pet is ill, pregnant or nursing.
Inputs
Daily feeding estimate
Daily water guide: –(estimated at 40–60 ml/kg/day; use the upper end in hot weather or with heavy exercise)
How it is calculated
- Resting energy: RER = 70 × weight(kg)^0.75
- Daily energy: DER = RER × life-stage factor × activity factor
- Total grams per day = DER ÷ energy density(kcal/100g) × 100
- Staple grams = total grams × (1 − treat share)
- Grams per meal = staple grams ÷ meals (3 for young, 2 for adults and seniors)
- Water = weight(kg) × 40–60 ml
DER factors and activity correction
| Situation | Factor |
|---|---|
| Young | 2.5 |
| Adult, neutered | 1.2 |
| Adult, intact | 1.4 |
| Senior | 1.1 |
| Weight loss (takes priority) | 0.8 |
| Situation | Factor |
|---|---|
| Young | 3.0 |
| Adult, neutered | 1.6 |
| Adult, intact | 1.8 |
| Senior | 1.4 |
| Weight loss (takes priority) | 1.0 |
Activity correction: low ×0.9, medium ×1.0, high ×1.1, applied after the life-stage factor.
Why the formula looks like this
Why weight^0.75
Energy use does not scale in a straight line with weight; it tracks body surface area more closely. Veterinary nutrition expresses this with metabolic weight, kg^0.75. The constant 70 is fitted from measured data, so a 4 kg cat has an RER near 198 kcal, not 4 × 70 = 280 kcal.
Why treats are subtracted
Treats and staple food draw from the same daily calorie budget. If you feed the full amount calculated from total energy and then add treats, intake goes above DER. Subtracting the treat share first keeps the total in range. A common guideline is to keep treats under 10% of daily calories.
Body condition score (BCS 1–9) and how to adjust
Run your hands along the ribs and look at the waistline: ribs easy to feel but not see, with a visible waist from above, usually means 4–5. Weight is only the starting point; body condition is the final check.
| BCS | Condition | Adjustment |
|---|---|---|
| 1–3 | Thin (ribs obvious, waist very tucked) | Add about 10% to the current amount, weigh every 1–2 weeks until back at 4–5. |
| 4–5 | Ideal (ribs easy to feel, waist visible) | Keep the current amount and weigh once a month; no change needed while weight is stable. |
| 6–9 | Overweight (ribs hard to feel, no waist) | Cut about 10%, or turn on weight-loss mode, and weigh every 2 weeks for a slow decline. |
Change the amount by about ±10% at a time; a sudden large cut can cause nutrient shortfalls or rebound.
7-day food transition
Sudden switches often cause loose stool or refusal. Mix the new food into the old one; if the stomach is sensitive, stretch each step by 1–2 days.
| Days | New food | Old food |
|---|---|---|
| Days 1–2 | 25% | 75% |
| Days 3–4 | 50% | 50% |
| Days 5–6 | 75% | 25% |
| Day 7 | 100% | 0% |
Five common mistakes
- Feeding by the bag
Bag charts usually give a weight-based range, assume an intact, moderately active pet, and differ in calorie density between brands. Combine neuter status, activity and body condition: calculate here, then fine-tune with BCS.
- Not counting treats
Treats count toward daily calories. One chew can take 10% of one day of energy while the staple portion stays the same, which leads to weight gain or an unbalanced diet over time.
- No reduction after neutering
Hormonal changes after neutering lower energy needs by roughly 10–20%, while appetite may rise. Feeding the old amount often leads to visible weight gain within six months.
- Switching to low-fat food just because of age
Senior pets need quality protein to keep muscle. Whether to go low-fat depends on body condition and health, not age alone; a sudden switch can also reduce how much they eat.
- Watching weight but not body condition
Two 5 kg pets can differ a lot in frame, muscle and body fat. Weight gives the starting calories; after that, ribs and waistline tell you whether to add or cut.
This tool does not provide diets for medical conditions. If your pet has kidney, diabetes, pancreatitis or other health issues, follow the calorie target and formula from a veterinarian.