This free cat water fountain size calculator tells you how big a water fountain your cats need, from cat count and daily water need, plus the reservoir size and how often you must refill it. It runs fully in your browser, so nothing you type is sent to a server, and you need no account and no sign-up to use it.
Many cat owners buy a pretty fountain that runs dry in a day, or a huge one that grows slime before it empties. The right reservoir covers two to four days of drinking, so water stays fresh without daily refills. Sizing it from real daily intake, not from the box picture, is what keeps cats drinking well.
Type the number of cats, the water each cat drinks per day in millilitres, and the fountain reservoir size, then press the calculate button. The tool shows daily use, days between refills, weekly use, and refills per week.
The result is a sizing guide, not a health check. Cats that suddenly drink far more or far less than usual should see a vet, because thirst change can signal illness. Always keep a plain bowl out too, in case the fountain pump fails.
Example: 2 cats drinking 220 ml each use 440 ml a day, so a 2,000 ml fountain lasts about 4.5 days and needs about 1.5 refills a week.
Clean the fountain weekly. Slime builds fast in warm rooms, and a weekly wash with a bottle brush keeps water tasting fresh.
Use filtered water if your tap water is hard. Hard water leaves scale on the pump, and scale is the main reason fountain pumps die early.
Place the fountain away from food. Cats prefer water away from their food bowl, and most cats drink more from a fountain in a separate spot.
Common question: How much water should a cat drink daily? About 50 ml per kilo of body weight, so a 4.5 kg cat needs near 220 ml a day, counting wet food water too.
Common question: Do cats really prefer running water? Many do. Running water stays oxygenated and tastes fresher, and moving water catches a cat eye far more than a still bowl.
Common question: What if my cat will not use the fountain? Let it run beside the old bowl for a week, with the old bowl slowly moved away. Most cats switch once the fountain water is the easy option.
Keep a simple notebook for a month. Write the numbers you used, the result, and what your cat did next. Did the cat sleep in the new bed, drink from the fountain, or walk calmly in the harness? That short record turns a vague feeling into clear evidence, and it makes the next adjustment much easier to judge.
A steady routine helps more than a perfect purchase. Feed at the same times, keep fresh water out, play at regular hours, and weigh your cat every few weeks. Cats settle well into routines, and a settled cat is easier to measure, easier to watch, and easier to keep healthy.
Finally, check the result against what you already own. If the new size is close to the old one, keep the old one. If it differs a lot, change in small steps and watch your cat for a week before you decide. Write both numbers down so you can compare them again later.
This tool is free to use as often as you like. Bookmark it, recheck the numbers when your cat grows, gains weight, or changes habits, and keep the daily routine steady. Small, steady habits matter far more for a cat than any single perfect number.