Feeding guides printed on packaging are treated by many owners as instructions. They are estimates built from averages, and the way they are constructed explains their known bias.
The equation underneath the table
Energy requirement is estimated from body weight using a standard relationship, because metabolic rate does not scale in a straight line with size.
That produces a resting requirement, which is then multiplied by a factor reflecting activity, life stage and whether the dog is neutered.
The result is divided by the food's energy density to give a weight of food per day. The printed table is that calculation performed across a range of weights.
Where the assumptions come from
The activity multipliers are population figures. They describe a typical dog in a category rather than any particular dog in a household.
Individual requirements around that average vary widely, and two dogs of identical weight and apparent activity can differ substantially in what they actually need.
Neutering lowers requirement noticeably, and many guides do not distinguish clearly, which alone accounts for a large share of gradual weight gain.
Why the numbers tend to run high
Guides are generally built around a more active assumption than most household dogs meet. A dog walked twice daily and otherwise resting sits below the typical multiplier.
Tables are also printed against ranges of weight rather than exact figures, and the amount for a range tends to suit the upper end of it.
There is also a commercial asymmetry: a guide that underfeeds produces visible complaints, while one that overfeeds produces slow weight gain nobody attributes to the packet.
What the table does not include
Treats, chews, training rewards and food used in enrichment toys are outside the calculation entirely, and together they often account for a substantial share of intake.
Dental chews in particular carry more energy than their size suggests, and a daily one can occupy a meaningful portion of a small dog's requirement.
Anything the dog eats counts towards the same budget, and the printed amount assumes it is the whole of it.
Using the guide as a starting point
The workable approach treats the table as an opening estimate and adjusts against the dog rather than the packet.
Body condition assessed by hand every few weeks, alongside weight recorded on the same scales, gives a far better signal than any calculation.
Weight change without a change in feeding, or an inability to maintain condition on a reasonable amount, is a veterinary question rather than a portioning one.