TL;DR: Most adult indoor cats need 200–250 calories per day. To calculate exact portions of wet and dry food, find the calorie density on your food packaging and divide your cat's daily calorie target by the ratio you want. The calculator below does the math for you — and the same numbers belong in writing with any cat sitter covering your cat while you travel.
Combining wet and dry food gives your cat the best of both: the hydration and palatability of wet food alongside the dental benefits and convenience of dry kibble. Getting the balance right means knowing how many calories your cat actually needs and what each food contributes — not just guessing based on what the packaging suggests, which is typically calibrated for an average cat rather than your specific one. If your cat has been struggling with constipation, adjusting wet food upward is often one of the first things to try — the cat constipation guide covers when and how.
Why combine wet and dry food
Wet food addresses the hydration gap. Cats evolved to get most of their moisture from prey and have a weak thirst drive — a cat eating only dry kibble often doesn't drink enough water to compensate. Wet food provides that moisture directly, which matters most for cats prone to urinary issues or kidney disease.
Dry food contributes to dental health through the mechanical action of chewing, and it is practically convenient — it can be left out without spoiling, which matters for cat owners who are out during the day or using a cat sitter for drop-in visits. A mixed diet captures both benefits without the compromises of relying entirely on either.
How many calories does your cat need
The baseline is 25 to 35 calories per pound of ideal body weight per day, or roughly 50 to 60 kcal per kilogram. For a typical indoor, spayed or neutered adult cat, this works out to 200 to 250 calories per day. Use your cat's ideal weight, not their current weight — if your cat is overweight, feeding to their actual weight will maintain the excess rather than reduce it.
Calorie needs vary by life stage and activity level. Kittens need more calories per kilogram than adults because they're growing. Senior cats generally need fewer overall calories but more protein to preserve muscle mass. Very active or outdoor cats burn more than sedentary indoor ones.
A spayed or neutered cat has a slower metabolic rate than an intact one — use the lower end of the range (50 kcal per kg) for neutered cats, and the higher end for intact, active, or younger animals.
How to calculate wet and dry food portions
The calculation has three steps: find your cat's daily calorie target, decide the ratio of wet to dry food, and convert each portion to grams or cans using the calorie density printed on the packaging. Look for the metabolizable energy (ME) figure — on dry food it is usually listed as kcal/cup or kcal/100g; on wet food it appears as kcal/can or kcal/kg.
Worked example: 4 kg (9 lb) cat, 70% dry / 30% wet split
Daily calorie target: 4 kg × 50 kcal = 200 kcal per day
Dry food portion (assume 350 kcal per 100 g):
200 kcal × 70% = 140 kcal from dry food
140 kcal ÷ 350 kcal × 100 = 40 g of dry food per day
Wet food portion (assume 80 kcal per 85 g can):
200 kcal × 30% = 60 kcal from wet food
60 kcal ÷ 80 kcal = 0.75 cans (about ¾ of a standard 85 g can) per day
When you add wet food to an existing dry-only diet, reduce the dry food proportionally so total calories stay the same. Adding wet food on top of a full dry food ration is one of the most common causes of gradual weight gain in cats.
Cat food portions calculator
Not a fan of the arithmetic? Use the calculator below — enter your cat's weight, activity level, and preferred wet-to-dry ratio, and it will calculate the exact daily portions for your specific foods.
How to split meals through the day
Using the 4 kg example above (40 g dry, ¾ can wet per day), a practical three-meal split would be:
- Morning: 20 g of dry food
- Afternoon: ¾ can of wet food
- Evening: 20 g of dry food
Wet food left out for more than two hours in warm conditions can spoil — serve it fresh and remove any uneaten portion rather than leaving it in the bowl. Dry food can be left accessible between scheduled meals, but measure the daily amount in the morning and use that as the total rather than free-filling throughout the day.
Golden rules for cat feeding
Always check the calorie density on the actual packaging. Formulas vary significantly between brands — a premium grain-free kibble may have 400 kcal per 100 g while a budget brand has 300 kcal per 100 g. Using the wrong figure can mean underfeeding or overfeeding by 25% or more even when you think you're being precise.
Treats count toward the daily calorie total. Keep supplemental treats and snacks under 10% of total daily calories — about 20 kcal for a 200 kcal/day cat. This is easier to track than it sounds once you know the numbers.
Monitor weight rather than portions alone. Cats should lose weight gradually if they need to — around 1% of body weight per week. If your cat is gaining or losing faster than expected, adjust portions by 10 to 15% and monitor over four weeks before adjusting again. Small, incremental changes produce better outcomes than large sudden reductions.
What to tell your cat sitter about feeding
The most common way cat feeding goes wrong during a cat sitting stay is vague instructions. "A bit of dry in the morning and some wet at night" leaves too much room for interpretation — your cat sitter may serve twice the intended amount without realising it. Written instructions with exact gram weights and can fractions take the guesswork out entirely.
Include in your cat sitter notes: the daily calorie target, the brand and variety of each food, the exact portion in grams or cans for each meal, what time meals should be served, and how long wet food can be left before it should be removed. If your cat is on a weight management plan or has a health condition requiring a specific diet, make this explicit — a cat sitter who doesn't know the context may not realise that filling the bowl generously is a problem. The pet sitter instructions guide covers the full range of information worth leaving for a cat sitter, with feeding as one of the most important sections.
For cat owners using Petme to find a cat sitter, bringing the calculated portion numbers to the meet-and-greet — not just "she eats twice a day" — is one of the most practical things you can do to ensure your cat's diet stays consistent while you're away.
Choosing quality wet food to pair with kibble
Look for wet food where a named protein source — chicken, salmon, tuna — appears as the first ingredient rather than derivatives or by-products. Avoid products with added sugars, artificial colors, or extensive filler ingredients. Wet food labeled "complete" provides a full nutritional profile on its own; "complementary" wet food is designed to be used alongside other foods and is not nutritionally complete as a standalone diet.
For a mixed wet-and-dry diet, choose complete wet food as the wet component. This gives you flexibility to adjust the wet-to-dry ratio without worrying about nutritional gaps. Once daily wet food serving is appropriate for most adult cats; more frequent small wet meals suit cats who prefer variety or those managing dental discomfort with dry food.
Frequently asked questions
1. How much wet and dry food combined should I feed my cat?
The total should meet your cat's daily calorie requirement — typically 200 to 250 calories for an average indoor neutered adult. Split those calories between wet and dry food in whatever ratio suits your cat's preferences and your routine, then calculate each portion from the calorie density on the packaging. The calculator above handles this automatically once you enter your cat's weight and preferred split.
2. What is the ratio of wet food to kibble?
There is no universal correct ratio — it depends on your cat's hydration needs, dental health, and preferences. A 50/50 split is a common starting point for cats with no specific health concerns. Cats prone to urinary issues or kidney disease benefit from a higher wet food proportion (70/30 or more). Cats with dental disease or weight management needs may do better with more dry food. Adjust the ratio as needed, keeping total calories constant.
3. What is the 25 rule for cat food?
The 25 rule refers to the minimum protein content recommendation for wet cat food on a dry matter basis — at least 25% protein content is considered a reasonable floor for quality wet food. It is not a portion guideline. When evaluating wet food labels, note that the protein percentage shown includes moisture, so the "as-fed" figure will appear lower than the actual protein content once moisture is removed. Higher-quality wet foods typically exceed 30% protein on a dry matter basis.
4. Is 85g of wet cat food enough?
It depends on the calorie density of that specific food and how much dry food your cat is also eating. A standard 85 g can typically contains 70 to 100 kcal. For a cat needing 200 kcal per day who also eats dry food, one 85 g can as the wet component of a mixed diet is generally appropriate. For a cat eating wet food only, one 85 g can per day would be far too little — most cats eating wet-only diets need three to four 85 g cans or equivalent per day.
5. Can I leave dry food out all day if I give wet food at set times?
Yes, but measure the daily dry allowance in the morning and use that as the total for the day rather than topping up freely. Free-feeding dry food alongside scheduled wet meals is one of the most reliable ways for cats to gradually gain weight, because the dry portion gets treated as unlimited rather than counted. For cat sitters managing a mixed feeding routine during a sitting stay, this is worth spelling out in your instructions rather than assuming it will be managed correctly.
6. Do portions change as my cat gets older?
Yes. Kittens need more calories per kilogram than adults. Adult cats typically need 50 to 60 kcal per kg of ideal weight. Senior cats (from around seven years) often need fewer total calories as activity decreases, but benefit from higher protein content to preserve muscle mass — standard "light" or "reduced calorie" formulas that are also low in protein can accelerate muscle loss in older cats. Adjust portions at each life stage and review with your vet at annual check-ups. 🐈
Getting your cat's food portions right is one of those small things that makes a meaningful difference to their health over the years. Once you have the numbers — daily calorie target, grams of dry, cans of wet — the routine runs itself. And when you hand that information to a cat sitter, you are giving them what they need to keep your cat's diet exactly as intended while you're away.
