Cat Size Calculator — Find How Big Will Your Kitten Get & Ideal Weight
Enter your cat’s breed, age, and current weight in cat size calculator to instantly predict their adult size, body condition score, and get personalized vet-approved health guidance — 100% free.
Cat Size Calculator
➡ Next step: Use our Cat Calorie Calculator to determine the exact daily calorie intake your cat needs based on this result.
How the Cat Size Calculator Works
Our kitten size calculator uses breed-specific maturity timelines, the 16-week growth landmark, and AVMA-referenced weight standards for 50+ breeds. Here’s what powers each result.
Breed-Specific Growth Timelines
Large breeds like Maine Coons and Ragdolls reach full size at 18–24 months; smaller breeds like Siamese finish at 12 months. Our calculator adapts predictions for each. Not sure of your cat’s breed? Our AI identifier can help before you calculate.
The 16-Week Growth Formula
Kittens reach roughly 50% of their adult weight by 4 months (16 weeks). We use this scientifically-established landmark — together with breed maturity age — to extrapolate predicted full-grown weight with high accuracy.
9-Point Body Condition Scoring
BCS is the gold standard vets use — more reliable than weight alone. We estimate your cat’s BCS range based on current weight relative to breed standard. Ideal is always BCS 4–5 on the 9-point scale.
Sex & Neuter Adjustments
Males are typically 2–5 lbs heavier than females. Spaying/neutering reduces metabolic rate by ~30%, raising obesity risk — our calculator accounts for both. Pair this with our Cat Calorie Calculator to adjust portions accordingly.
🔗 Not sure what breed your cat is? Breed affects everything — size range, growth speed, and ideal weight. Use these tools first:
Cat Weight Chart by Breed — Healthy Ranges
Reference data from the Association for Pet Obesity Prevention (APOP), The International Cat Association (TICA), and Cornell Feline Health Center. Don’t know your cat’s breed? Our AI breed identifier can confirm it before you compare against these benchmarks.
Sources: APOP Ideal Weight Ranges (2024); TICA Breed Standards; Cornell Feline Health Center. Female ranges are typically 2–5 lbs lower.
| Breed | Size | Male (lbs) | Female (lbs) | Full Grown By | BCS Ideal |
|---|---|---|---|---|---|
| Maine Coon | XL | 15–25 | 10–15 | 18–24 months | 4–5 / 9 |
| Ragdoll | XL | 15–20 | 10–15 | 18–24 months | 4–5 / 9 |
| Siberian | Large | 12–20 | 8–12 | 18 months | 4–5 / 9 |
| Norwegian Forest Cat | Large | 13–22 | 9–15 | 18 months | 4–5 / 9 |
| British Shorthair | Large | 12–18 | 9–15 | 15 months | 4–5 / 9 |
| Savannah | Large | 12–25 | 10–16 | 15 months | 4–5 / 9 |
| Bengal | Medium | 10–15 | 8–12 | 12 months | 4–5 / 9 |
| Persian | Medium | 9–14 | 7–12 | 12 months | 4–5 / 9 |
| American Shorthair | Medium | 10–15 | 8–12 | 12 months | 4–5 / 9 |
| Domestic Shorthair (Mixed) | Medium | 10–14 | 8–11 | 12 months | 4–5 / 9 |
| Siamese | Small–Med | 11–15 | 8–12 | 12 months | 4–5 / 9 |
| Abyssinian | Small–Med | 8–12 | 6–10 | 12 months | 4–5 / 9 |
| Devon Rex | Small | 6–10 | 5–8 | 12 months | 4–5 / 9 |
| Singapura | Small | 6–8 | 4–6 | 12 months | 4–5 / 9 |
📌 If you’re unsure which breed row applies to your cat, use our free AI Cat Breed Identifier to confirm before comparing. Mixed-breed cats may fall between rows.
Kitten Growth Stages — Month-by-Month Guide
Kittens grow fastest in their first 6 months, then growth slows significantly. Understanding these stages helps you predict adult size and ensure proper nutrition at each phase. If your cat is pregnant, our Cat Pregnancy Calculator can help track healthy weight gain during gestation.
Source: Cornell Feline Health Center kitten growth standards & AVMA veterinary references (2024). Curve represents average domestic mixed-breed cat.
| Age | Avg Weight (Domestic) | % of Adult Size | Growth Phase | Key Milestone |
|---|---|---|---|---|
| 0–2 weeks | 0.2–0.4 lbs | ~3% | Neonatal | Eyes/ears closed; fully dependent on mother |
| 4 weeks | 0.8–1.0 lbs | ~8% | Transitional | Eyes open; beginning to sample solid food |
| 8–12 weeks | 1.0–2.0 lbs | 15–20% | Socialization | Typical adoption age; first vaccinations |
| 4 months (16 wks) | 2.5–4.0 lbs | ~50% | Rapid Growth | Half of adult weight reached — best prediction point |
| 6 months | 4–6 lbs | 65–75% | Juvenile | Spay/neuter recommended; growth begins slowing |
| 9–10 months | 7–9 lbs | 85–90% | Sub-adult | Near adult height; still filling out in muscle |
| 12 months | 8–11 lbs | ~100% (small breeds) | Adult | Most breeds reach full adult size |
| 18–24 months | 10–25 lbs (breed-dependent) | 100% | Adult | Large breeds (Maine Coon, Ragdoll, Siberian) finish growing |
| 7+ years | Varies | — | Senior | Weight monitoring critical; senior vet checkup recommended |
Feeding the right calories at each growth stage matters as much as the food itself. Use our Cat Calorie Calculator to determine exact daily calorie needs by life stage, and our Cat Water Intake Calculator to ensure proper hydration alongside healthy growth.
Feline Body Condition Score (BCS) — Visual Guide
The 9-point BCS system is the gold standard veterinary method for assessing cat weight — more reliable than scale weight alone because it accounts for muscle mass, frame size, and coat. Research shows 58% of cat owners incorrectly assess their cat’s body condition (Journal of Veterinary Internal Medicine, 2022).
Severely Underweight
Ribs, spine, and hip bones visibly prominent. Severe muscle wasting. Requires urgent veterinary care.
Underweight
Ribs easily felt with minimal fat. Visible waist and abdominal tuck. Increase caloric intake.
✅ Ideal
Ribs palpable under a thin fat layer. Visible waist from above. Minimal belly fat. Perfect condition.
Overweight
Ribs hard to feel. Slight waist visible. Rounded abdomen. Reduce calories; increase play sessions.
Obese
Ribs cannot be felt. No visible waist. Heavy abdominal fat. Consult a vet for a weight loss plan.
Source: Association for Pet Obesity Prevention (APOP) 2024 National Pet Obesity Survey. 59% of domestic cats are overweight or obese.
Overweight cats need fewer calories — but calculating the right deficit matters. Use our Cat Calorie Calculator to find the correct daily intake for safe, gradual weight loss (the AAHA-recommended 1–2% body weight per week). Pair with our Cat Litter Calculator — overweight cats often struggle with litter box access and benefit from lower-entry boxes and correct box sizing.
What Determines a Cat’s Adult Size?
Cat adult size is driven by a combination of genetic, hormonal, and environmental factors. Understanding these helps set accurate expectations for your kitten’s growth and prevents misdiagnosing a healthy cat as overweight or underweight.
| Factor | Impact | Key Details | What to Do |
|---|---|---|---|
| Breed & Genetics | 🔴 Very High | Largest single factor. Maine Coons reach 25 lbs; Singapuras stay at 4–8 lbs. Genetics sets the ceiling and floor. | Identify your cat’s breed first for accurate size expectations. |
| Sex | 🟠 High | Males average 2–5 lbs heavier than females of the same breed due to larger skeletal frame and muscle mass. | Select correct sex in the calculator above for accurate ideal weight range. |
| Spay / Neuter | 🟡 Moderate | Reduces metabolic rate by ~30%. Does not cause larger growth — but significantly raises obesity risk post-surgery. | Reduce food portions 10–20% post-surgery. Use our Calorie Calculator for adjusted targets. |
| Kittenhood Nutrition | 🟡 Moderate | Malnourished kittens may not reach their genetic size potential. Overfeeding does not create bigger cats — just fatter ones. | Feed high-protein kitten food until 12 months (18–24 months for large breeds). Track water intake too. |
| Indoor vs. Outdoor | 🟢 Low–Moderate | Indoor cats trend slightly heavier due to lower activity and more consistent feeding schedules. | Add 15 mins of interactive play daily. Puzzle feeders and cat trees help indoor cats maintain healthy weight. |
| Paw Size | 🟢 Weak Indicator | Larger paws can loosely hint at a larger adult size, but are not a reliable standalone predictor. | Use paw size as a secondary signal alongside breed identification — not as a primary sizing method. |
Complete Cat Health & Care Toolkit
Cat size and weight don’t exist in a vacuum — they connect directly to nutrition, hydration, litter, and breeding health. Use these free tools together for a complete picture of your cat’s wellbeing.
Frequently Asked Questions
Common questions about predicting cat adult size, tracking kitten growth, healthy weight ranges, and understanding body condition scoring.
Scientific References & Data Sources
All data, weight ranges, and formulas used in this calculator and guide are derived from peer-reviewed veterinary research and established feline health authorities.
Referenced Sources
- Association for Pet Obesity Prevention (APOP). 2024 National Pet Obesity Prevalence Survey. apop.us.
- Cornell Feline Health Center. Kitten Growth and Development Standards. vet.cornell.edu. 2024.
- The International Cat Association (TICA). Breed Standard Weight Ranges. tica.org. 2024.
- American Veterinary Medical Association (AVMA). Body Condition Scoring Guidelines for Cats. avma.org. 2023.
- American Animal Hospital Association (AAHA). Nutritional Assessment Guidelines for Dogs and Cats. 2024.
- Journal of Veterinary Internal Medicine. Owner accuracy in assessing feline body condition — epidemiological study. 2022.
- Laflamme, D.P. Development and validation of a body condition score system for cats. Feline Practice 25(5-6):13-18, 1997.
- Courcier, E.A. et al. Epidemiological study of environmental factors associated with feline obesity. Journal of Small Animal Practice, 2010.