Mixing Dry and Wet Food: Calculating the Grams of Each and How Much Water

The trick is to divide by calories, not grams

If you try to mix dry and wet half and half by weight, it goes wrong. Dry and wet differ by about 4 times in calories per 100 g, and the reason is their water content.

100 g of wet food has only the calories of about 23 g of dry. So "50 g dry + 50 g wet" has far fewer calories than 100 g of dry alone, and conversely, "the usual dry + 1 pouch of wet" has more calories than usual. To set amounts, first decide how to split the daily calories between dry and wet, then convert each to grams.

How to calculate amounts when mixing

1. 1

   Find the daily calories

   Multiply the RER (70 × weight^0.75) by a factor. For a spayed or neutered 4 kg cat, that's about 238 kcal. With 10% going to treats, about 214 kcal is left for food.

2. 2

   Decide the calorie split

   For a split of 70% dry and 30% wet, for example, assign about 150 kcal to dry and about 64 kcal to wet.

3. 3

   Convert each to grams

   Dry (380 kcal/100 g): 150 ÷ 380 × 100 ≈ 39 g. Wet (85 kcal/100 g): 64 ÷ 85 × 100 ≈ 75 g.

Chart by ratio (4 kg spayed or neutered cat)

Out of about 238 kcal a day, this divides the roughly 214 kcal left after 10% for treats between dry (380 kcal/100 g) and wet (85 kcal/100 g). Pouches are calculated at 70 g each.

The idea is the same for dogs. For a spayed or neutered 10 kg dog (about 630 kcal a day), dividing the roughly 567 kcal left after 10% for treats into 80% dry (360 kcal/100 g) and 20% wet (85 kcal/100 g) gives about 126 g of dry and about 133 g of wet. Dry alone would be about 158 g, so adding the wet means reducing the dry by about 32 g.

Working back when you want to use up one pouch

Calculating from a ratio tends to give awkward amounts like "0.7 of a pouch." If you want to use up an opened pouch, it's easier to fix the wet amount first and fill the rest with dry.

1. 1

   Find the wet food's calories

   A 70 g pouch (85 kcal/100 g) is 70 × 0.85 = about 60 kcal. If the package states the calories per pouch, use that.

2. 2

   Subtract from the calories for food

   For a 4 kg cat (about 214 kcal for food), 214 − 60 = about 154 kcal is left for dry.

3. 3

   Convert the dry to grams

   154 ÷ 380 × 100 ≈ 41 g. One pouch plus about 41 g of dry makes a day's food. With 2 pouches, the dry is about 25 g.

How much to drink: subtract the moisture in wet food

A handy rule is that a dog's or cat's daily water need in ml is about the same as its daily calorie need in kcal. That's about 238 ml for a spayed or neutered 4 kg cat, and about 630 ml for a spayed or neutered 10 kg dog. Per kg of body weight, it's about 63 ml for a 10 kg dog and about 59 ml for a 4 kg cat.

This water can also come from food, though. Dry food is about 10% water and wet food about 78%, so the more wet food a pet eats, the less it needs to drink from the bowl.

• If your pet stops drinking after switching to wet food, it's because the food is supplying the water, and in most cases there's nothing to worry about.
• Cats naturally drink little. If a mostly dry-fed cat drinks little, try mixing in wet food or adding more bowls to get more water into it.
• If a dog keeps drinking over 100 ml per kg of body weight a day, or a cat over 50 ml, it can be a sign of kidney disease or diabetes. Talk to a veterinarian.

Calculate mixed amounts and water with the tool

In the Dog & Cat Food Portion Calculator's "Daily food amount" tab, use "+ Mix foods" to add a second or third food. Enter the type (dry, wet or semi-moist), calories, calorie share and the weight of one can or pouch to see how many grams of each per day and per meal, and how many cans that makes. The "Treats and water" tab shows how much to expect from the bowl after subtracting food moisture. How to think about daily calories is covered in How Many Grams of Dog Food a Day? for dogs and How Many Grams of Cat Food a Day? for cats.

FAQ

How much should I reduce dry food when mixing in wet?

Reduce the dry by the same calories as the wet you add. Adding a 70 g pouch (about 60 kcal) means reducing 380 kcal/100 g dry by about 16 g. For a spayed or neutered 4 kg cat, about 56 g of dry becomes about 41 g (after subtracting 10% for treats).

What amounts make a half-and-half mix of dry and wet?

Halve by calories, not weight. For a spayed or neutered 4 kg cat, split the roughly 214 kcal for food in two, for about 28 g of dry (380 kcal/100 g) and about 126 g of wet (85 kcal/100 g).

How much water should dogs and cats drink a day?

The daily water need in ml is about the same as the daily calorie need in kcal. Subtract the water in food (about 10% for dry, about 78% for wet) to get the amount from the bowl. For a 4 kg cat, that's about 232 ml on dry only and about 41 ml on wet only.

My pet stopped drinking after switching to wet food. Is that OK?

Wet food is about 80% water, so the food alone often supplies most of the water needed, and drinking less is natural. If energy, appetite and urine volume haven't changed, there's no need to worry.

Can toppers cause weight gain?

Yes. Add a pouch (about 60 kcal) to a 4 kg cat's diet without reducing the dry, and daily calories rise by about 25%. When you add a topper, take the same calories out of the dry food.