Water is the one nutrient a cat cannot store, and the arithmetic is short: 40 to 60 mL per kg of body weight per day, counting food, bowl and everything in between. A 4 kg cat needs 160 to 240 mL in 24 hours; a 6 kg cat needs 240 to 360 mL. Measure that for 3 days with a marked bottle and most worries about drinking stop being guesses.
Two more numbers decide whether that total is being handled well: urine specific gravity above 1.060, which means the kidney still concentrates properly, and 3 trips to the litter box a day in normal volumes. The third is 5 percent, where dehydration becomes visible at home and a vet visit stops being optional.
The 40-60 mL/kg band is a range for a reason
The low end fits a quiet, neutered adult in a 20 C room eating wet food. The high end fits an active cat in a 28 C apartment, a cat on dry food only, or a cat that spends 4 hours a day chasing a housemate. Move up 10 to 20 percent in summer and in centrally heated flats in winter, where indoor humidity can sit at 25 to 30 percent.
Life stage shifts the band further. Kittens under 16 weeks run 60 to 80 mL/kg because their surface area is large relative to weight. A nursing queen can take 2 to 3 times her normal intake and still look flat. A cat with chronic kidney disease (CKD) may lose 30 to 50 mL/kg of urine a day through poor concentration, so a normal-looking bowl intake can coexist with mild dehydration.
Wet food and dry food: the 78 percent difference
Moisture content does most of the work before the cat ever drinks. A typical pouch is 78 to 82 percent water, so 85 g of food delivers 66 to 70 mL. Dry kibble sits at 8 to 10 percent, so 60 g delivers 5 to 6 mL, roughly a tenth as much. That single gap explains why dry-fed cats drink 3 to 5 times more from the bowl, and why a dry-fed cat that stops drinking is a 24-hour problem rather than a 3-day one.
Metabolism adds 10 to 15 mL of water per 100 kcal, so a 4 kg cat eating 200 kcal gains 20 to 30 mL that never passes the bowl. The table converts the band into bowl targets, assuming wet food covers about 80 percent of the total and dry food about 15 percent.
| Cat weight | Total at 40 mL/kg | Total at 60 mL/kg | Bowl target, wet-fed (about 20%) | Bowl target, dry-fed (about 85%) |
|---|---|---|---|---|
| 3 kg | 120 mL | 180 mL | 24-36 mL | 102-153 mL |
| 4 kg | 160 mL | 240 mL | 32-48 mL | 136-204 mL |
| 5 kg | 200 mL | 300 mL | 40-60 mL | 170-255 mL |
| 6 kg | 240 mL | 360 mL | 48-72 mL | 204-306 mL |
Counting bowl intake takes 30 seconds a day. Fill a 500 mL bottle each morning and refill bowls only from it. At the same hour the next day, read what is left; the difference is intake, plus or minus 10 to 20 mL for spillage. Three days of that gives an average to compare with the table.
Urine specific gravity: 1.060 is the line worth knowing
A clinic refractometer reads from 1.000 to 1.060 in under a minute, and a cat's normal concentrated range is 1.035 to 1.060. Above 1.060 the kidney is doing excellent work with little water. Between 1.020 and 1.034 concentration is only moderate, which is common on wet food and worth repeating. A reading of 1.008 to 1.012 is isosthenuria: the kidney is no longer concentrating at all, and that finding needs bloodwork, not a bigger bowl.
One dilute sample proves little. A wet meal, a long drink or a stressful car ride can pull a single reading down to 1.015. Repeat 2 samples 7 days apart before drawing a conclusion, and check 2 to 3 times a year in cats over 7, or every 6 months once CKD stage 1 or 2 is on the record. Owners who track numbers catch the drop from 1.055 to 1.025 months before creatinine moves.
Three urinations a day: the volume check
Normal output is 20 to 30 mL per kg per day, which shows up as 2 to 4 clumps of 40 to 60 g in clumping litter, or 3 trips to the box in 24 hours for a cat that prefers to go outside the box less often. A 5 kg cat producing 100 to 150 mL of urine a day is squarely normal.
Change in pattern is the signal, not the absolute count. Six to 8 small clumps with straining suggests cystitis. A male cat crouching for 6 to 8 hours with nothing produced is a blocked urethra and a same-hour emergency, not a wait-and-see. Drinking above 100 mL/kg a day, with urine that looks pale, points toward diabetes or thyroid disease and needs a panel within 48 hours.
Reading 5 percent dehydration at home
Five percent means 5 percent of body weight, so 250 mL in a 5 kg cat. At that level the skin tent over the shoulders returns in 2 to 3 seconds instead of under 1 second, gums feel tacky rather than slick, and capillary refill runs 2 to 3 seconds. A kitchen scale is the most honest tool: 100 g lost in one day is 2 percent of a 5 kg cat, and 250 g in a week is 5 percent.
Replacement volume is calculated by the vet as the deficit plus maintenance, usually given over 12 to 24 hours, and the route depends on how well the cat is holding food down. What you can do at home is offer 5 to 10 mL of water by syringe every 30 minutes, or switch 1 of 2 daily meals to wet food, which adds 60 to 70 mL per pouch without any persuasion at all.
When the numbers say call the vet
- Bowl intake above 100 mL/kg per day for 3 days, with large pale clumps.
- No urine for 6 to 8 hours in a male cat, with crying or repeated squatting.
- Weight down 5 percent in 7 days, or 10 percent in 30 days.
- Urine specific gravity at 1.012 or below on 2 samples 7 days apart.
- Vomiting 3 or more times in 12 hours, or any refusal of water for 24 hours.
Five habits that move the number this week
Weigh the cat on the same kitchen scale every Sunday and write it down; a 100 g drift is easy to explain, a 400 g drift is not. Add a second bowl in a different room, because many cats drink 20 to 40 percent more when water is not next to food. Change bowl water at 12-hour intervals, since water sitting 24 hours is often refused, and try a 3 mm stream from a tap for cats that ignore still water.
Finally, put the litter box count and the bowl count on the same note: 2 columns, 30 seconds a day. Related reading: feline color vision and white blood cell counts. Still choosing a cat? The breed quiz covers the size differences that shift every mL/kg figure above.
Terms mentioned in this article
Frequently asked
My cat drinks almost nothing but seems fine. Is that normal?
It is normal on wet food. A pouch at 78 to 82 percent moisture supplies 66 to 70 mL, so a 4 kg cat eating 2 pouches can reach 140 mL from food alone before touching the bowl. On dry food the same cat needs 136 to 204 mL from the bowl, and drinking almost nothing for 3 days is a reason to measure intake and check urine specific gravity rather than to relax.
What urine specific gravity should worry me?
Above 1.060 is good concentration. Between 1.035 and 1.060 is the normal band. A reading of 1.008 to 1.012 on 2 samples taken 7 days apart means the kidney is not concentrating at all, and that calls for bloodwork including creatinine, SDMA and thyroid. One dilute sample after a wet meal or a long drink proves nothing, so always repeat before acting.
How do I check for 5 percent dehydration without a vet?
Weigh the cat on a kitchen scale: 250 g lost in a 5 kg cat is 5 percent. Then check the skin tent over the shoulders, which should spring back in under 1 second when hydrated and takes 2 to 3 seconds at 5 percent, plus tacky gums and capillary refill of 2 to 3 seconds. Any cat at 5 percent with vomiting or no urine for 6 to 8 hours needs a vet the same day.
Related guides
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- Cat Stomach pH: 1.5-2.0 Fasting and the 2-Hour Rebound
- Cat Gut Transit Time: 24 to 36 Hours, Measured 2 Ways
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