How much water does a cat need per day?

Cats need approximately 50 ml of water per kilogram of body weight per day. A 4.5 kg (10 lb) cat needs about 225 ml of water daily. This includes water from food — wet food is ~80% water, dry food is ~10% water.

How do I know if my cat is dehydrated?

Signs of dehydration in cats include lethargy, dry gums, loss of skin elasticity (skin tenting), sunken eyes, and decreased urination. Cats on dry-food-only diets are at highest risk. Use our hydration calculator to see if your cat gets enough water from food.

Why does my cat not drink enough water?

Cats evolved from desert wildcats and have a naturally low thirst drive — they are biologically programmed to get most of their water from prey, not standing water. In the wild, a mouse is ~70% water, so cats never needed to drink frequently. Modern dry kibble at only 10% moisture creates a chronic low-grade dehydration state. Solutions include: switching to wet food or adding water to dry food, using a cat water fountain (cats prefer moving water), placing multiple water bowls around the house (away from food and litter boxes), and flavoring water with tuna juice or low-sodium broth. A hydrated cat produces more dilute urine, which reduces the risk of FLUTD and kidney disease.

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Cat Hydration Calculator

Calculate how much water your cat needs daily. Accounts for moisture from dry food and wet food.

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主要な知識

How Much Water Should a Cat Drink?

Cats need 50-60 ml water per kg body weight per day. A 5 kg cat needs ~250-300 ml total, from both drinking and food moisture. Cats need 50-60 ml of water per kg of body weight per day. A 5 kg cat needs ~250-300 ml total daily water intake. But this comes from TWO sources: drinking water + moisture in food. Wet food is ~80% water; dry food is only ~10%. A cat eating primarily dry food must drink significantly more than one eating wet food.

出典： NRC Nutrient Requirements of Cats

Why Cats Are Prone to Dehydration

Cats evolved from desert wildcats and have a low thirst drive — they're biologically programmed to get water from prey, not a bowl. Domestic cats evolved from desert-dwelling wildcats (Felis silvestris lybica) and have a low thirst drive — they're biologically programmed to get most of their water from prey. In the wild, a mouse is ~70% water. Modern dry kibble at 10% moisture creates a chronic low-grade dehydration state that contributes to kidney disease and FLUTD (lower urinary tract disease).

出典： Anderson — Feline Hydration Research

Dehydrated Cat Symptoms

Early signs: lethargy, dry gums, skin tenting (pinch shoulder skin — if slow to snap back, dehydrated), decreased appetite and urination. Early signs: lethargy, dry/tacky gums, decreased appetite, and skin tenting (gently pinch skin between shoulder blades — if it doesn't snap back immediately, dehydration is likely). Advanced signs: sunken eyes, increased heart rate, constipation, panting. If you see these signs, contact your vet. Chronic low-grade dehydration is silent but damages kidneys over time.

出典： AAFP Senior Care Guidelines

Wet Food vs. Dry Food Hydration

Wet food (80% moisture): ~160 ml water from 200g of food. Dry food (10% moisture): only ~10 ml. Dry-fed cats must drink 200+ ml more daily. A cat eating only wet food (80% moisture) at 200g/day gets ~160 ml water just from food — already 50-60% of daily needs. The same cat on dry food (10% moisture) gets only ~10 ml. The remaining 200+ ml must come from drinking. Cats on dry food need to drink proportionally more — and many don't, leading to concentrated urine and higher kidney/U.T. disease risk.

出典： AAFP Feline Nutrition Research

petsMetricsが査読付き獣医ソースを使用して検証したデータ。引用：ASPCA、AVMA、AAFP。最終レビュー：2026。

The Science Behind the Cat Hydration Calculator

The NRC formula for feline daily water requirement is: Total H₂O (ml) = Weight (kg) × 50 ml/kg. Food moisture is calculated as: DryFood_g × 0.10 + WetFood_g × 0.80. Additional drinking water needed = Total H₂O − Food H₂O. This two-source model is critical because cats' evolutionary biology gives them a low thirst drive — they depend on food moisture. The 50 ml/kg constant comes from NRC (2006) feline nutrient requirements and is validated against healthy cat water turnover studies.

References: NRC Nutrient Requirements of Cats (2006); AAFP Feline Nutrition Guidelines— via petsMetrics

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