Comparing cost per serving between kibble and wet food

The displayed price almost always refers to the pack or the kilo of product, and that figure alone tells you nothing useful. The reason is simple: different products have different energy density, meaning they supply a different amount of energy for the same weight. A very concentrated food needs little, a more dilute one needs far more, and the real cost depends on how much product actually ends up in the bowl each day.

Wet food takes this effect to the extreme because it contains a lot of water. You are paying per kilo for a product that is largely liquid, so the price per unit of weight is inevitably high but says nothing about the cost per serving. Kibble, by contrast, is dehydrated and concentrated, so far less of it covers the same requirement. Comparing the two prices per kilo means comparing apples with oranges.

The calculation is simpler than it looks and you do it once per product. You need three pieces of information: the animal's energy requirement, the energy the product supplies per unit of weight and the price of the pack. With these three numbers you reach the cost of a single day, which is the only truly comparable figure.

1. 1

   Start from the animal's energy requirement

   How much energy your animal uses in a day is the starting point. You can estimate it with the vet based on weight, age, activity and body condition. Without this number every comparison hangs in the air.

2. 2

   Read the energy the product declares

   On the label you find how much energy the product supplies per unit of weight. If it is not stated directly, ask the maker or choose products that declare it: without this figure you cannot work out the real ration.

3. 3

   Work out the daily ration in grams

   Divide the animal's requirement by the energy the product supplies per gram. You get how many grams of that product are needed each day, which is the true amount you use, not the one suggested by eye on the pack.

4. 4

   Derive the cost per gram from the pack

   Divide the pack price by its weight in grams. It is the only way to compare different sizes, because a large pack and a small one have different prices per gram even for the same product.

5. 5

   Multiply to get the daily cost

   Multiply the grams per day by the cost per gram. The result is what you spend each day to feed the animal on that product, and it is the number you can finally compare between kibble and wet food.

6. 6

   Repeat for each product and tabulate

   Run the same calculation for every candidate food and line up the daily costs. A small table makes it obvious in seconds which option weighs most on the monthly budget.

The numbers below are an illustrative example to show the method, not real values for specific products. The aim is to show you how price per kilo and daily cost can tell opposite stories, and why only the second should be used to decide.

Once you can read the cost per day, you can work to bring it down with practical choices that do not touch the food's adequacy. It is not about buying the cheapest product, but about paying less for the same nutritional value.

• Compare cost per gram across sizes: large packs often cost less per gram, but only if you can use them before they expire.
• Consider a mixed solution of kibble and wet food, which can lower the daily cost compared with wet food alone while keeping some of its benefits.
• Weigh the rations instead of guessing: oversized portions are wasted money and, over time, a weight problem.
• Count snacks and treats in the calculation, because they are calories that add to the cost and should be subtracted from the ration.
• Record the food spend month by month, so you see the real effect of a product change instead of estimating it from memory.