Use our free cat BMI calculator to check whether your cat is underweight, ideal, overweight, or obese — based on body weight, body condition score (BCS), and breed size. Includes a personalised daily calorie target for weight loss or maintenance.
What Is a Healthy Weight for a Cat?
Most domestic cats have a healthy weight of 8–10 lb (3.6–4.5 kg), but ideal weight varies by breed, sex, and body frame. A large Maine Coon may be healthy at 18 lb, while a petite Siamese is ideal at 6–8 lb. Weight alone is less accurate than a Body Condition Score (BCS) — the vet-standard method for assessing feline body composition.
| Breed Type | Typical Healthy Weight (Female) | Typical Healthy Weight (Male) |
|---|---|---|
| Small breeds (Singapura, Devon Rex) | 4–6 lb (1.8–2.7 kg) | 5–8 lb (2.3–3.6 kg) |
| Medium breeds (DSH, Siamese, Abyssinian) | 6–9 lb (2.7–4.1 kg) | 8–12 lb (3.6–5.4 kg) |
| Large breeds (Ragdoll, Norwegian Forest) | 10–15 lb (4.5–6.8 kg) | 12–20 lb (5.4–9.1 kg) |
| Maine Coon | 8–12 lb (3.6–5.4 kg) | 13–18 lb (5.9–8.2 kg) |
Cat Body Condition Score (BCS): The Real Cat BMI
Unlike humans, cats don’t have a direct BMI formula. Vets use the 9-point Body Condition Score (BCS) scale developed by Purina, which assesses fat coverage over ribs, spine, and waist definition. This is the most accurate way to assess your cat’s weight status at home.
| BCS Score | Category | What You Feel & See | Action |
|---|---|---|---|
| 1–2 | Severely underweight | Ribs, spine, and hip bones clearly visible with no fat cover. Severe muscle loss. | Vet visit immediately |
| 3 | Underweight | Ribs easily visible, minimal fat cover, obvious waist and abdominal tuck. | Increase calories; vet check |
| 4–5 | ✅ Ideal | Ribs easily felt with slight fat cover. Visible waist from above. Abdominal tuck present. | Maintain current diet |
| 6–7 | Overweight | Ribs felt with firm pressure. Waist barely visible. Slight abdominal rounding. | Reduce calories 10–20% |
| 8–9 | Obese | Ribs very difficult to feel. No waist. Heavy abdominal fat pad. Fat deposits on neck and limbs. | Vet-supervised weight loss |
How to Check Your Cat’s BCS at Home
- Rib check: Run your fingers along your cat’s ribcage with light pressure. You should be able to feel individual ribs easily — like running your hand over the back of your own knuckles. If you have to press hard to find them, your cat is overweight. If they protrude visibly, your cat is underweight.
- Waist check: Look at your cat from above. There should be a visible narrowing behind the ribs — a defined waist. No visible waist = overweight.
- Abdominal tuck: Look at your cat from the side. The belly should tuck upward behind the ribcage. A sagging belly or prominent fat pad = overweight or obese.
Cat Weight Status Calculator by Current Weight
Use this quick reference to estimate your cat’s weight status by current body weight for a typical domestic shorthair:
| Current Weight | Likely Status (DSH / average cat) | Estimated Ideal Weight |
|---|---|---|
| Under 5 lb (2.3 kg) | Underweight | 7–9 lb depending on frame |
| 6–9 lb (2.7–4.1 kg) | ✅ Ideal (female) / Low-normal (male) | Maintain |
| 8–11 lb (3.6–5 kg) | ✅ Ideal (male) | Maintain |
| 12–14 lb (5.4–6.4 kg) | Overweight | Target 9–11 lb |
| 15–17 lb (6.8–7.7 kg) | Obese | Target 9–11 lb (gradual loss) |
| 18 lb+ (8.2 kg+) | Severely obese | Vet-supervised plan required |
Cat Weight Loss Calorie Calculator
If your cat is overweight, safe weight loss requires a calorie reduction — never starving, as cats can develop hepatic lipidosis (fatty liver disease) when food is restricted too severely.
Safe weight loss calorie formula:
- Calculate RER at your cat’s ideal body weight (not current): RER = 70 × (ideal weight in kg)^0.75
- Multiply by 0.8 for weight loss
- Never feed less than the RER at ideal weight (no multiplier)
| Ideal Target Weight | RER (kcal/day) | Weight Loss Target (0.8× RER) | Maintenance (1.2× RER) |
|---|---|---|---|
| 7 lb (3.2 kg) | 168 kcal | 134 kcal/day | 202 kcal/day |
| 8 lb (3.6 kg) | 185 kcal | 148 kcal/day | 222 kcal/day |
| 9 lb (4.1 kg) | 203 kcal | 163 kcal/day | 244 kcal/day |
| 10 lb (4.5 kg) | 218 kcal | 175 kcal/day | 262 kcal/day |
| 11 lb (5 kg) | 234 kcal | 187 kcal/day | 281 kcal/day |
Target weight loss rate: 0.5–2% of body weight per week. For a 15 lb cat targeting 10 lb, expect 6–12 months of gradual loss under veterinary supervision.
Health Risks of Feline Obesity
Obesity is the most common preventable disease in cats. An overweight or obese cat is at significantly higher risk of:
- Type 2 diabetes mellitus — overweight cats are 4× more likely to develop diabetes
- Hepatic lipidosis (fatty liver disease) — can develop within days of food restriction or illness in obese cats
- Osteoarthritis — excess weight accelerates joint damage, especially in older cats
- Urinary tract disease (FLUTD) — obesity is a major risk factor for feline lower urinary tract disease
- Heart disease — hypertrophic cardiomyopathy risk increases with excess body fat
- Reduced lifespan — studies show obese cats live on average 2.5 years less than healthy-weight cats
How to Help Your Cat Lose Weight
- Switch to a measured diet: Stop free-feeding. Weigh food with a kitchen scale — cup measurements are inaccurate by up to 80%.
- Use a weight management food: High-protein, low-carb, calorie-controlled formulas (e.g., Hill’s Prescription Diet r/d, Royal Canin Satiety) are most effective.
- Split meals: Feed 2–4 small meals per day. Puzzle feeders slow eating and increase mental stimulation.
- Increase activity: 2 × 10-minute interactive play sessions daily burn calories and reduce boredom eating.
- Monthly weigh-ins: Track progress monthly. A food scale at home makes this easy — weigh yourself holding and not holding the cat, subtract the difference.
- Work with your vet: For cats over BCS 7, a vet-supervised weight loss plan with regular check-ins is strongly recommended to avoid hepatic lipidosis.
Frequently Asked Questions
How do I calculate my cat’s BMI?
Cats don’t use a BMI formula the way humans do. The veterinary equivalent is the Body Condition Score (BCS) — a 9-point scale assessed by feeling your cat’s ribs, observing their waist from above, and checking for an abdominal tuck from the side. A BCS of 4–5 is ideal. BCS 6–7 is overweight; BCS 8–9 is obese.
What is a healthy weight for a cat?
Most domestic cats are healthy at 8–10 lb (3.6–4.5 kg), but ideal weight varies by breed and sex. Petite breeds like Siamese may be healthy at 6–8 lb, while large breeds like Maine Coons can be healthy at 13–18 lb. Focus on body condition score rather than a single weight number for the most accurate assessment.
How many calories should an overweight cat eat per day?
For safe weight loss, feed your cat 80% of their RER calculated at their ideal (target) body weight — not their current weight. For most cats targeting 9–10 lb, this works out to approximately 140–175 kcal per day. Never restrict below the RER without veterinary guidance, as severe restriction can cause hepatic lipidosis.
Is my cat fat or just big-boned?
Do the rib check: place your hands on your cat’s sides and feel for ribs with light finger pressure. If you can feel them easily (like knuckles under skin), your cat is a healthy weight. If you have to press firmly or can’t feel them at all, your cat is overweight regardless of frame size. A visible waist from above and abdominal tuck from the side are the clearest signs of healthy weight.
How long does it take for a cat to lose weight?
Safe feline weight loss is slow — target 0.5–2% of body weight per week. A cat losing 1% per week at 14 lb targeting 10 lb would take approximately 20–25 weeks (5–6 months). Faster weight loss increases the risk of hepatic lipidosis. Patience and consistency are essential; most cats reach their target weight within 6–12 months.