Dog food calculator: how much should your dog eat?

Vets estimate a dog’s energy needs in two steps. First comes the resting energy requirement, the calories a dog burns lying still: 70 multiplied by body weight in kilograms raised to the power of 0.75. That exponent matters, because a 40 kg dog does not need four times the food of a 10 kg dog, only about 2.8 times.

The resting figure is then multiplied by a factor for real life. A typical neutered pet sits around 1.6, an intact adult a little higher, a very active dog near 2, and young puppies around 3 because they are building bone and muscle every day. For weight loss the factor drops to about 1.0, applied to the target weight rather than the current one.

Calories become grams through the energy density of the food. Dry foods usually carry 330 to 420 kcal per 100 g, wet foods far less because most of the weight is water. That is why the calculator asks for the figure on your bag: the same dog could need 250 g of one kibble and 300 g of another.

Cups are a rough guide only. A cup of small, dense kibble can weigh 30 percent more than a cup of large, airy pieces, so a cheap kitchen scale is the single best feeding tool you can buy.

Numbers are a starting point. Every two to four weeks, run your hands along your dog’s ribs: you should feel them easily under a thin layer, and see a waist from above. If the ribs are hard to find, cut portions by about 10 percent; if they are sharp and visible, add 10 percent and recheck.